Synthesis Method of Organometallic Complex, Synthesis Method of Pyrazine Derivative, 5,6-Diaryl-2-Pyrazyl Triflate, Light-Emitting Element, Light-Emitting Device, Electronic Device, and Lighting Device

ABSTRACT

Provided is a 5,6-diaryl-2-pyrazyl triflate, its synthetic method, and a method for synthesizing an organometallic complex having a triarylpyrazine ligand from the 5,6-diaryl-2-pyrazyl triflate. The triflate is readily obtained from the corresponding 5,6-diarylpyrazin-2-ol, and the palladium-catalyzed coupling of the 5,6-diaryl-2-pyrazyl triflate with an arylboronic acid derivative leads to a high yield of a triarylpyrazine derivative having high purity. The use of the triarylpyrazine derivative in the reaction with a metal compound such as a metal chloride results in an ortho-metallated organometallic complex with high purity. The high purity of the organometallic complex contributes to the extremely high durability of a light-emitting element.

BACKGROUND OF THE INVENTION

1. Field of the Invention

One embodiment of the present invention relates to a novel method forsynthesizing an organometallic complex such as an organoiridium complex.Another embodiment of the present invention relates to a novel methodfor synthesizing a triarylpyrazine derivative. Another embodiment of thepresent invention relates to 5,6-diaryl-2-pyrazyl triflate used for theabove synthesis methods. Another embodiment of the present inventionrelates to a light-emitting element, a light-emitting device, anelectronic device, and a lighting device each including anorganometallic complex synthesized by the above synthesis method.

Note that one embodiment of the present invention is not limited to theabove technical field. Specifically, examples of the technical field ofone embodiment of the present invention disclosed in this specificationinclude a semiconductor device, a display device, a liquid crystaldisplay device, a light-emitting device, a lighting device, and a methodfor manufacturing any of them.

2. Description of the Related Art

A light-emitting element in which an EL layer is provided between a pairof electrodes is a self-luminous light-emitting element in whichcarriers (holes and electrons) are injected from the pair of electrodesby application of an electric field and recombined in the EL layer togenerate energy, so that light is emitted.

An organic compound is mainly used as an EL material for an EL layer ina light-emitting element and greatly contributes to an improvement inthe characteristics of the light-emitting element. For this reason,novel organic compounds improved from various angles have beendeveloped. When the organic compound contains impurities such as ahalogen element, the characteristics of the light-emitting elementdeteriorate. To solve this problem, element characteristics are improvedby reducing impurities by purification by sublimation (e.g., PatentDocument 1).

REFERENCE Patent Document [Patent Document 1] Japanese Published PatentApplication No. 2011-216903 SUMMARY OF THE INVENTION

However, purification by sublimation cannot necessarily removeimpurities easily in synthesis of organic compounds. When a materialused in a synthesis process contains a substance which potentially actsas an impurity, it is sometimes technically difficult to make an endproduct impurity-free. Thus, to reduce impurities in an organiccompound, it is important to establish a synthesis method that does notresult in a substance that can be an impurity in a synthesis process.

In view of the above backdrop, one embodiment of the present inventionprovides a novel 5,6-diaryl-2-pyrazyl triflate as an organic compoundthat realizes a synthesis method which negligibly gives impurities.Another embodiment of the present invention provides a method forsynthesizing an organometallic complex such as an organoiridium complexin which the above 5,6-diaryl-2-pyrazyl triflate is used. Anotherembodiment of the present invention provides a method for synthesizing atriarylpyrazine derivative in which the above 5,6-diaryl-2-pyrazyltriflate is used. Another embodiment of the present invention provides alight-emitting element, a light-emitting device, an electronic device,or a lighting device using an organometallic complex obtained by theabove synthesis method as an EL material. Another embodiment of thepresent invention provides a novel light-emitting element, a novellight-emitting device, a novel lighting device, or the like. Note thatthe descriptions of these objects do not disturb the existence of otherobjects. In one embodiment of the present invention, there is no need toachieve all the objects. Other objects will be apparent from and can bederived from the description of the specification, the drawings, theclaims, and the like.

One embodiment of the present invention is a novel synthesis method bywhich the content of halogen such as chlorine that potentially acts asan impurity is reduced and an organometallic complex can be obtainedefficiently. Specifically, in this method, a triarylpyrazine derivativeis formed with the use of novel 5,6-diaryl-2-pyrazyl triflate, and thenan organometallic complex with reduced halogen content is synthesized.

That is, one embodiment of the present invention is a synthesis methodof an organometallic complex which includes the following steps: a stepof coupling a 5,6-diaryl-2-pyrazyl triflate and an arylboronic acid toform a 2,3,5-triarylpyrazine derivative that is a triarylpyrazinederivative; a step of reacting the 2,3,5-triarylpyrazine derivative witha metal compound containing halogen to form a dinuclear complex; and astep of reacting the dinuclear complex with a ligand.

Another embodiment of the present invention is a synthesis method of anorganometallic complex which includes the following steps: a step ofcoupling a 5,6-diaryl-2-pyrazyl triflate having a structure representedby General Formula (G0) and an arylboronic acid to form a2,3,5-triarylpyrazine derivative that is a triarylpyrazine derivative; astep of reacting the 2,3,5-triarylpyrazine derivative with a metalcompound containing halogen to form a dinuclear complex; and a step ofreacting the dinuclear complex with a ligand. Note that, in theaforementioned embodiments, the organometallic complex is exemplified byan ortho-metallated complex, and iridium, platinum, rhodium, and thelike are given as the metal.

In General Formula (G0), R¹ to R⁸ each independently represent any oneof hydrogen, an alkyl group having 1 to 6 carbon atoms, a phenyl group,and a phenyl group having, as a substituent, an alkyl group having 1 to6 carbon atoms.

Note that the above synthesis method enables high-yield synthesis of theorganometallic complexes using an inexpensive material and reduces thecontent of chlorine that potentially acts as an impurity; thus, thesynthesis method is suitable for mass synthesis, for example.

Another embodiment of the present invention is a 5,6-diaryl-2-pyrazyltriflate with a structure represented by General Formula (G0) which canbe used in the above synthesis method.

In General Formula (G0), R¹ to R⁸ each independently represent any oneof hydrogen, an alkyl group having 1 to 6 carbon atoms, a phenyl group,and a phenyl group having, as a substituent, an alkyl group having 1 to6 carbon atoms.

Other embodiments of the present invention are a light-emitting elementusing an organometallic complex synthesized by the above synthesismethod, and a light-emitting device including the light-emittingelement.

Note that one embodiment of the present invention includes not only alight-emitting device including the light-emitting element but also anelectronic device and a lighting device each including thelight-emitting device. The light-emitting device in this specificationrefers to an image display device and a light source (e.g., a lightingdevice). In addition, the light-emitting device includes, in itscategory, all of a module in which a light-emitting device is connectedto a connector such as a flexible printed circuit (FPC), a tape carrierpackage (TCP), a module in which a printed wiring board is provided onthe tip of a TCP, and a module in which an integrated circuit (IC) isdirectly mounted on a light-emitting element by a chip on glass (COG)method.

One embodiment of the present invention makes it possible to provide anovel method for synthesizing an organometallic complex in which a5,6-diaryl-2-pyrazyl triflate that is a novel organic compound is used.Another embodiment of the present invention enables the production of a5,6-diaryl-2-pyrazyl triflate that is a novel organic compound. Notethat this novel organic compound does not contain a substance that canbe an impurity during the synthesis by the above synthesis method,thereby reducing impurities in the organometallic complex that is an endproduct. Another embodiment of the present invention allows theformation of a highly reliable light-emitting element, a highly reliablelight-emitting device, a highly reliable electronic device, or a highlyreliable lighting device using an organometallic complex synthesized bythe above synthesis method as an EL material. Another embodiment of thepresent invention is capable of providing a novel light-emittingelement, a novel light-emitting device, a novel lighting device, or thelike. Note that the description of these effects does not disturb theexistence of other effects. In one embodiment of the present invention,there is no need to obtain all the effects. Other effects will beapparent from and can be derived from the description of thespecification, the drawings, the claims, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a structure of a light-emitting element.

FIGS. 2A and 2B each illustrate a structure of a light-emitting element.

FIGS. 3A and 3B illustrate a light-emitting device.

FIGS. 4A to 4D illustrate electronic devices.

FIG. 5 illustrates lighting devices.

FIG. 6 is a ¹H-NMR chart of 5,6-bis(3,5-dimethylphenyl)-2-pyrazyltriflate obtained in Step 2 in Example 1.

FIG. 7 is a ¹H-NMR chart of5-(2,6-dimethylphenyl)-2,3-bis(3,5-dimethylphenyl)pyrazine (Hdmdppr-dmp)obtained in Step 3 in Example 1.

FIG. 8 is a ¹H-NMR chart of an organometallic complex represented byStructural Formula (300).

FIG. 9 is a ¹H-NMR chart of 5,6-diphenyl-2-pyrazyl triflate obtained inStep 2 in Example 2.

FIG. 10 is a ¹H-NMR chart of 2,3,5-triphenylpyrazine (Htppr) obtained inStep 3 in Example 2.

FIG. 11 is a ¹H-NMR chart of an organometallic complex represented byStructural Formula (310).

FIG. 12 is a ¹H-NMR chart of 5,6-diphenyl-2-pyrazyl triflate obtained inStep 3 in Example 3.

FIG. 13 is a ¹H-NMR chart of an organometallic complex represented byStructural Formula (312).

FIG. 14 shows an ultraviolet-visible absorption spectrum and an emissionspectrum of an organometallic complex represented by Structural Formula(312).

FIG. 15 shows LC/MS measurement results of an organometallic complexrepresented by Structural Formula (312).

FIG. 16 is a ¹H-NMR chart of 5,6-bis(4-methylphenyl)-2-pyrazyl triflaterepresented by Structural Formula (105).

FIG. 17 is a ¹H-NMR chart of an organometallic complex represented byStructural Formula (301).

FIG. 18 shows luminance-current efficiency characteristics of Element 1and Reference Element 1.

FIG. 19 shows luminance-external quantum efficiency characteristics ofElement 1 and Reference Element 1.

FIG. 20 shows voltage-luminance characteristics of Element 1 andReference Element 1.

FIG. 21 shows normalized emission spectra of Element 1 and ReferenceElement 1.

FIG. 22 shows time-normalized luminance curves of Element 1 andReference Element 1.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of the present invention will be described withreference to the accompanying drawings. Note that the present inventionis not limited to the following description, and various changes andmodifications can be made without departing from the spirit and scope ofthe present invention. Therefore, the present invention should not beconstrued as being limited to the description in the followingembodiments.

Embodiment 1

In this embodiment, a method for synthesizing an organometallic complexthat is one embodiment of the present invention is described.Hereinafter, the explanation is mainly given to a synthetic method of anorganoiridium complex. However, the embodiment is not limited to thesynthetic method of an organoiridium complex but includes those of anorganoplatinum complex, an organorhodium complex, and the like.

One embodiment of the present invention is a synthesis method thatincludes a synthetic pathway to a novel 5,6-diaryl-2-pyrazyl triflate,which is a synthetic intermediate, thereby producing an organometalliccomplex with reduced chlorine content in a high yield.

<<Synthesis Method of 5,6-Diaryl-2-Pyrazyl Triflate Represented byGeneral Formula (G0)>>

First, a synthesis method of 5,6-diaryl-2-pyrazyl triflate representedby General Formula (G0) is described.

The novel 5,6-diaryl-2-pyrazyl triflate (General Formula (G0)) issynthesized in the following manner. As shown in Synthesis Scheme (A-1)below, a 1,2-diaryl diketone (General Formula (a1)) and glycinamidehydrochloride are reacted to obtain a compound represented by GeneralFormula (a2); then, a hydroxyl group of the compound represented byGeneral Formula (a2) is transformed to a triflate group usingtrifluoromethanesulfonic anhydride (abbreviation: Tf₂O) in the presenceof a weak base.

In Synthesis Scheme (A-1), R¹ to R⁸ each independently represent any oneof hydrogen, an alkyl group having 1 to 6 carbon atoms, a phenyl group,and a phenyl group having, as a substituent, an alkyl group having 1 to6 carbon atoms.

Note that the above 5,6-diaryl-2-pyrazyl triflate is a novel compound ofone embodiment of the present invention that is useful in synthesizingorganometallic complexes. Since a wide variety of the compounds (GeneralFormula (a1) and General Formula (a2)) used in Synthesis Scheme (A-1)are commercially available or can be readily synthesized, many kinds ofthe 5,6-diaryl-2-pyrazyl triflate (General Formula (G0)) can besynthesized by the above synthesis method. Shown below are specificstructural formulae of the 5,6-diaryl-2-pyrazyl triflate represented byGeneral Formula (G0) (Structural Formulae (100) to (111)). Note that oneembodiment of the present invention is not limited thereto.

<<Synthesis Method of Triarylpyrazine Derivative Represented by GeneralFormula (G1)>>

Then, as illustrated in Synthesis Scheme (A-2), the 5,6-diaryl-2-pyrazyltriflate (General Formula (G0)) and an arylboronic acid (General Formula(a3)) are coupled with each other, whereby a triarylpyrazine derivativehaving an aryl group as a substituent (General Formula (G1)) issynthesized.

In Synthesis Scheme (A-2), R¹ to R¹³ each independently represent anyone of hydrogen, an alkyl group having 1 to 6 carbon atoms, a phenylgroup, and a phenyl group having, as a substituent, an alkyl grouphaving 1 to 6 carbon atoms.

Shown below are specific structural formulae of the triarylpyrazinederivative represented by General Formula (G1) and synthesized underSynthesis Scheme (A-2) (Structural Formulae (200) to (213)). Note thatone embodiment of the present invention is not limited thereto.

As described above, the 5,6-diaryl-2-pyrazyl triflate synthesized underSynthesis Scheme (A-1) is produced to contain no chlorine. As a result,the triarylpyrazine derivative synthesized under Synthesis Scheme (A-2)using the 5,6-diaryl-2-pyrazyl triflate can also be produced to containno chlorine.

<<Synthesis Method of Organometallic Complex Represented by GeneralFormula (G2)>>

Next, a synthesis method of an organometallic complex represented byGeneral Formula (G2) and synthesized using the triarylpyrazinederivative is described.

In General Formula (G2), R¹ to R¹³ each independently represent any oneof hydrogen, an alkyl group having 1 to 6 carbon atoms, a phenyl group,and a phenyl group having, as a substituent, an alkyl group having 1 to6 carbon atoms. Further, L represents a monoanionic ligand, and Mrepresents iridium, platinum, or rhodium. Hereinafter, explanation isgiven to the case where M is iridium.

First, as shown in Synthesis Scheme (A-3-1), the pyrazine derivativerepresented by General Formula (G1) and an iridium compound whichcontains halogen (e.g., iridium chloride, iridium bromide, or iridiumiodide) are reacted under an inert gas atmosphere in the absence of asolvent or in an alcoholic solvent (e.g., glycerol, ethylene glycol,2-methoxyethanol, or 2-ethoxyethanol) alone, or a mixed solvent of waterand an alcoholic solvent, whereby a dinuclear complex (P), which is onetype of an organoiridium complex including a halogen-bridged structure,is obtained.

In Synthesis Scheme (A-3-1), R¹ to R¹³ each independently represent anyone of hydrogen, an alkyl group having 1 to 6 carbon atoms, a phenylgroup, and a phenyl group having, as a substituent, an alkyl grouphaving 1 to 6 carbon atoms. In addition, Y represents halogen.

There is no particular limitation on the temperature of the reaction ofSynthesis Scheme (A-3-1), and the reaction can be conducted underheating. When heating is conducted, an oil bath, a sand bath, or analuminum block may be used. Alternatively, microwaves can be used as aheating source.

Then, as shown in Synthesis Scheme (A-3-2), the dinuclear complex (P)obtained under Synthesis Scheme (A-3-1) is reacted with a ligand HL inan inert gas atmosphere, whereby a proton of the ligand HL isdissociated and a monoanionic ligand L coordinates to the iridium. Thus,the organoiridium complex represented by General Formula (G3) can beobtained.

In Synthesis Scheme (A-3-2), R¹ to R¹³ each independently represent anyone of hydrogen, an alkyl group having 1 to 6 carbon atoms, a phenylgroup, and a phenyl group having, as a substituent, an alkyl grouphaving 1 to 6 carbon atoms. Further, L represents a monoanionic ligand.

There is no particular limitation on the temperature of the reaction ofSynthesis Scheme (A-3-2), and the reaction can be conducted underheating. When heating is conducted, an oil bath, a sand bath, or analuminum block may be used. Alternatively, microwaves can be used as aheating source.

Shown below are specific structural formulae of the organoiridiumcomplex represented by General Formula (G2) and synthesized underSynthesis Scheme (A-3-2) (Structural Formulae (300) to (315)). Note thatone embodiment of the present invention is not limited thereto.

The above-described organometallic complex obtained by the synthesismethod of one embodiment of the present invention can emitphosphorescence and thus can be used as a light-emitting material or alight-emitting substance of a light-emitting element.

An organometallic complex with reduced impurities can be synthesized bythe synthesis method of one embodiment of the present invention. Thus,by using the organometallic complex as an EL material, a light-emittingelement, a light-emitting device, an electronic device, or a lightingdevice having high emission efficiency and high reliability can beprovided. Furthermore, an organometallic complex can be synthesized in ahigh yield by the synthesis method of one embodiment of the presentinvention, which enables stable supply of the material and a reductionin cost of a light-emitting element, a light-emitting device, anelectronic device, a lighting device, or the like that includes thematerial.

Note that the structure described in this embodiment can be combined asappropriate with any of the structures described in the otherembodiments.

Embodiment 2

In this embodiment, a light-emitting element in which the organometalliccomplex obtained by the synthesis method of one embodiment of thepresent invention is used as an EL material is described with referenceto FIG. 1.

In a light-emitting element described in this embodiment, as illustratedin FIG. 1, an EL layer 102 including a light-emitting layer 113 isinterposed between a pair of electrodes (a first electrode (anode) 101and a second electrode (cathode) 103), and the EL layer 102 includes ahole-injection layer 111, a hole-transport layer 112, anelectron-transport layer 114, an electron-injection layer 115, and thelike in addition to the light-emitting layer 113.

When voltage is applied to such a light-emitting element, holes injectedfrom the first electrode 101 side and electrons injected from the secondelectrode 103 side recombine in the light-emitting layer 113 to lead alight-emitting substance contained in the light-emitting layer 113 to anexcited state. The light-emitting substance in the excited state emitslight when it returns to the ground state.

Although the organometallic complex synthesized by the synthesis methodof one embodiment of the present invention can be used for any one ormore layers in the EL layer 102 described in this embodiment, theorganometallic complex is preferably used for the light-emitting layer113. In other words, the organometallic complex is used in part of alight-emitting element having a structure described below.

A specific example for fabricating the light-emitting element describedin this embodiment is described below.

As the first electrode 101 and the second electrode 103, a metal, analloy, an electrically conductive compound, a mixture thereof, and thelike can be used. Specific examples are indium oxide-tin oxide (indiumtin oxide (ITO)), indium oxide-tin oxide containing silicon or siliconoxide, indium oxide-zinc oxide (indium zinc oxide), indium oxidecontaining tungsten oxide and zinc oxide, gold (Au), platinum (Pt),nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe),cobalt (Co), copper (Cu), palladium (Pd), and titanium (Ii). Inaddition, an element belonging to Group 1 or Group 2 of the periodictable, for example, an alkali metal such as lithium (Li) or cesium (Cs),an alkaline earth metal such as calcium (Ca) or strontium (Sr),magnesium (Mg), an alloy containing such an element (MgAg, AlLi), a rareearth metal such as europium (Eu) or ytterbium (Yb), an alloy containingsuch an element, graphene, and the like can be used. The first electrode101 and the second electrode 103 can be formed by, for example, asputtering method or an evaporation method (including a vacuumevaporation method).

The hole-injection layer 111 injects holes into the light-emitting layer113 through the hole-transport layer 112 with a high hole-transportproperty. The hole-injection layer 111 contains a substance with a highhole-transport property and an acceptor substance, so that electrons areextracted from the substance with a high hole-transport property by theacceptor substance to generate holes and the holes are injected into thelight-emitting layer 113 through the hole-transport layer 112. Thehole-transport layer 112 is formed using a substance with a highhole-transport property.

Specific examples of the substance with a high hole-transport property,which is used for the hole-injection layer 111 and the hole-transportlayer 112, include aromatic amine compounds such as4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB orα-NPD),N,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1′-biphenyl]-4,4′-diamine(abbreviation: TPD), 4,4′,4″-tris(carbazol-9-yl)triphenylamine(abbreviation: TCTA), 4,4′,4″-tris(N,N-diphenylamino)triphenylamine(abbreviation: TDATA),4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine(abbreviation: MTDATA), and4,4′-bis[N-(spiro-9,9′-bifluoren-2-yl)-N-phenylamino]biphenyl(abbreviation: BSPB);3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA1);3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA2); and3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole(abbreviation: PCzPCN1). Other examples include carbazole derivativessuch as 4,4′-di(N-carbazolyl)biphenyl (abbreviation: CBP),1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (abbreviation: TCPB), and9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA).The substances listed here are mainly ones that have a hole mobility of10⁻⁶ cm²/Vs or higher. Note that any substance other than the substanceslisted here may be used as long as the hole-transport property is higherthan the electron-transport property.

A high molecular compound such as poly(N-vinylcarbazole) (abbreviation:PVK), poly(4-vinyltriphenylamine) (abbreviation: PVTPA),poly[N-(4-{N′-[4-(4-diphenylamino)phenyl]phenyl-N′-phenylamino}phenyl)methacrylamide](abbreviation:PTPDMA), orpoly[N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl)benzidine](abbreviation:Poly-TPD) can also be used.

Examples of the acceptor substance that is used for the hole-injectionlayer 111 include oxides of metals belonging to Groups 4 to 8 of theperiodic table. Specifically, molybdenum oxide is particularlypreferable.

The light-emitting layer 113 is a layer containing a light-emittingsubstance. The light-emitting layer 113 may contain only alight-emitting substance; alternatively, a light-emitting substance(guest material) may be dispersed in a host material in thelight-emitting layer 113. Note that a substance that has high tripletexcitation energy is preferably used as the host material. As alight-emitting substance, the organometallic complexes shown inEmbodiment 1 can be used.

The material that can be used as the light-emitting substance in thelight-emitting layer 113 is exemplified by, in addition to theaforementioned organometallic complex, a light-emitting substanceconverting singlet excitation energy into luminescence or alight-emitting substance converting triplet excitation energy intoluminescence. In this case, the light-emitting substance may be locatedin the same layer as or in a different layer from the organometalliccomplex. Examples of the light-emitting substance are given below.

As an example of the light-emitting substance converting singletexcitation energy into luminescence, a substance emitting fluorescencecan be given.

Examples of the substance emitting fluorescence includeN,N′-bis[4-(9H-carbazol-9-yl)phenyl]-N,N′-diphenylstilbene-4,4′-diamine(abbreviation: YGA2S),4-(9H-carbazol-9-yl)-4′-(10-phenyl-9-anthryl)triphenylamine(abbreviation: YGAPA),4-(9H-carbazol-9-yl)-4′-(9,10-diphenyl-2-anthryl)triphenylamine(abbreviation: 2YGAPPA),N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: PCAPA), perylene, 2,5,8,11-tetra(tert-butyl)perylene(abbreviation: TBP),4-(10-phenyl-9-anthryl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBAPA),N,N″-(2-tert-butylanthracene-9,10-diyldi-4,1-phenylene)bis[N,N′,N′-triphenyl-1,4-phenylenediamine](abbreviation: DPABPA),N,9-diphenyl-N-[4-(9,10-diphenyl-2-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: 2PCAPPA),N-[4-(9,10-diphenyl-2-anthryl)phenyl]-N,N′,N′-triphenyl-1,4-phenylenediamine(abbreviation: 2DPAPPA),N,N,N′,N′,N″,N″,N′″,N′″-octaphenyldibenzo[g,p]chrysene-2,7,10,15-tetraamine(abbreviation: DBC1), coumarin 30,N-(9,10-diphenyl-2-anthryl)-N,9-diphenyl-9H-carbazol-3-amine(abbreviation: 2PCAPA),N-[9,10-bis(1,1′-biphenyl-2-yl)-2-anthryl]-N,9-diphenyl-9H-carbazol-3-amine(abbreviation: 2PCABPhA),N-(9,10-diphenyl-2-anthryl)-N,N′,N′-triphenyl-1,4-phenylenediamine(abbreviation: 2DPAPA),N-[9,10-bis(1,1′-biphenyl-2-yl)-2-anthryl]-N,N′,N′-triphenyl-1,4-phenylenediamine(abbreviation: 2DPABPhA),9,10-bis(1,1′-biphenyl-2-yl)-N-[4-(9H-carbazol-9-yl)phenyl]-N-phenylanthracen-2-amine(abbreviation: 2YGABPhA), N,N,9-triphenylanthracen-9-amine(abbreviation: DPhAPhA), coumarin 545T, N,N′-diphenylquinacridone(abbreviation: DPQd), rubrene,5,12-bis(1,1′-biphenyl-4-yl)-6,11-diphenyltetracene (abbreviation: BPT),2-(2-{2-[4-(dimethylamino)phenyl]ethenyl}-6-methyl-4H-pyran-4-ylidene)propanedinitrile (abbreviation: DCM1),2-{2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile(abbreviation: DCM2),N,N,N′,N′-tetrakis(4-methylphenyl)tetracene-5,11-diamine (abbreviation:p-mPhTD),7,14-diphenyl-N,N,N′,N′-tetrakis(4-methylphenyl)acenaphtho[1,2-a]fluoranthene-3,10-diamine(abbreviation: p-mPhAFD),{2-isopropyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[i]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile(abbreviation: DCJTI),{2-tert-butyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile(abbreviation: DCJTB),2-(2,6-bis{2-[4-(dimethylamino)phenyl]ethenyl}-4H-pyran-4-ylidene)propanedinitrile(abbreviation: BisDCM), and2-{2,6-bis[2-(8-methoxy-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile(abbreviation: BisDCJTM).

Examples of the light-emitting substance converting triplet excitationenergy into luminescence include a substance emitting phosphorescenceand a thermally activated delayed fluorescence (TADF) material. Notethat “delayed fluorescence” exhibited by the TADF material refers tolight emission having the same spectrum as normal fluorescence but anextremely long lifetime. The lifetime is 10⁻⁶ seconds or longer,preferably 10⁻³ seconds or longer.

Examples of the substance emitting phosphorescence includebis{2-[3′,5′-bis(trifluoromethyl)phenyl]pyridinato-N,C^(2′)}iridium(III)picolinate (abbreviation: Ir(CF₃ppy)₂(pic)),bis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)]iridium(III)acetylacetonate (abbreviation: FIracac),tris(2-phenylpyridinato)iridium(III) (abbreviation: Ir(ppy)₃),bis(2-phenylpyridinato)iridium(III) acetylacetonate (abbreviation:Ir(ppy)₂(acac)), tris(acetylacetonato)(monophenanthroline)terbium(II)(abbreviation: Tb(acac)₃(Phen)), bis(benzo[h]quinolinato)iridium(III)acetylacetonate (abbreviation: Ir(bzq)₂(acac)),bis(2,4-diphenyl-1,3-oxazolato-N,C^(2′))iridium(III) acetylacetonate(abbreviation: Ir(dpo)₂(acac)),bis{2-[4′-(perfluorophenyl)phenyl]pyridinato-N,C^(2′)}iridium(II)acetylacetonate (abbreviation: Ir(p-PF-ph)₂(acac)),bis(2-phenylbenzothiazolato-N,C^(2′))iridium(III) acetylacetonate(abbreviation: Ir(bt)₂(acac)),bis[2-(2′-benzo[4,5-a]thienyl)pyridinato-N,C^(3′)]iridium(III)acetylacetonate (abbreviation: Ir(btp)₂(acac)),bis(1-phenylisoquinolinato-N,C^(2′))iridium(III) acetylacetonate(abbreviation: Ir(piq)₂(acac)),(acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III)(abbreviation: Ir(Fdpq)z(acac)),(acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinato)iridium(III)(abbreviation: [Ir(mppr-Me)₂(acac)]),(acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinato)iridium(III)(abbreviation: [Ir(mppr-iPrh(acac)]),(acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III)(abbreviation: [Ir(tBuppm)₂(acac)]),(acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III)(abbreviation: [Ir(dppm)₂(acac)]),2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum(II)(abbreviation: PtOEP), tris(1,3-diphenyl-1,3-propanedionato)(monophenanthroline)europium(III) (abbreviation: Eu(DBM)₃(Phen)), andtris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III)(abbreviation: Eu(TA)₃(Phen)).

Preferable examples of the substance (i.e., host material) used fordispersing the light-emitting substance converting triplet excitationenergy into luminescence include compounds having an arylamine skeleton,such as 2,3-bis(4-diphenylaminophenyl)quinoxaline (abbreviation: TPAQn)and NPB, carbazole derivatives such as CBP and4,4′,4″-tris(carbazol-9-yl)triphenylamine (abbreviation: TCTA), andmetal complexes such as bis[2-(2-hydroxyphenyl)pyridinato]zinc(abbreviation: Znpp₂), bis[2-(2-hydroxyphenyl)benzoxazolato]zinc(abbreviation: Zn(BOX)₂),bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum (abbreviation:BAlq), and tris(8-quinolinolato)aluminum (abbreviation: Alq₃).Alternatively, a high molecular compound such as PVK can be used.

Examples of the TADF material include a fullerene, a derivative thereof,an acridine derivative such as proflavine, and eosin. Other examplesinclude a metal-containing porphyrin, such as a porphyrin containingmagnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium(In), or palladium (Pd). Examples of the metal-containing porphyrininclude a protoporphyrin-tin fluoride complex (SnF₂(Proto IX)), amesoporphyrin-tin fluoride complex (SnF₂(Meso IX)), ahematoporphyrin-tin fluoride complex (SnF₂(Hemato IX)), a coproporphyrintetramethyl ester-tin fluoride complex (SnF₂(Copro III-4Me)), anoctaethylporphyrin-tin fluoride complex (SnF₂(OEP)), anetioporphyrin-tin fluoride complex (SnF₂(Etio I)), and anoctaethylporphyrin-platinum chloride complex (PtCl₂OEP). Alternatively,a heterocyclic compound including a π-electron rich heteroaromatic ringand a π-electron deficient heteroaromatic ring can be used, such as2-(biphenyl-4-yl)-4,6-bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1,3,5-triazine(PIC-TRZ). Note that a material in which the π-electron richheteroaromatic ring is directly bonded to the π-electron deficientheteroaromatic ring is particularly preferably used because both thedonor property of the π-electron rich heteroaromatic ring and theacceptor property of the π-electron deficient heteroaromatic ring areincreased and the energy difference between the S₁ level and the T₁level is decreased.

When a host material and the organometallic complex described inEmbodiment 1 are included in the light-emitting layer 113 in thepresence or absence of any of the light-emitting substances convertingsinglet excitation energy into luminescence or any of the light-emittingsubstances converting triplet excitation energy into luminescence (i.e.,a guest material), light emission with high emission efficiency can beobtained from the light-emitting layer 113.

The electron-transport layer 114 is a layer containing a substance witha high electron-transport property. For the electron-transport layer114, a metal complex such as Alq₃,tris(4-methyl-8-quinolinolato)aluminum (abbreviation: Almq₃),bis(10-hydroxybenzo[h]quinolinato)beryllium (abbreviation: BeBq₂), BAlq,Zn(BOX)₂, or bis[2-(2-hydroxyphenyl)benzothiazolato]zinc (abbreviation:Zn(BTZ)₂) can be used. A heteroaromatic compound such as2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene(abbreviation: OXD-7),3-(4′-tert-butylphenyl)-4-phenyl-5-(4″-biphenyl)-1,2,4-triazole(abbreviation: TAZ),3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazole(abbreviation: p-EtTAZ), bathophenanthroline (abbreviation: Bphen),bathocuproine (abbreviation: BCP), or4,4′-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: BzOs) can alsobe used. A high molecular compound such as poly(2,5-pyridinediyl)(abbreviation: PPy),poly[(9,9-dihexylfluorene-2,7-diyl)-co-(pyridine-3,5-diyl)](abbreviation:PF-Py) orpoly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,2′-bipyridine-6,6′-diyl)](abbreviation:PF-BPy) can also be used. The substances listed here are mainly onesthat have an electron mobility of 1×10⁻⁶ cm²/Vs or higher. Note that anysubstance other than the substances listed here may be used for theelectron-transport layer 114 as long as the electron-transport propertyis higher than the hole-transport property.

The electron-transport layer 114 is not limited to a single layer, butmay be a stack of two or more layers each containing any of thesubstances listed above.

The electron-injection layer 115 is a layer containing a substance witha high electron-injection property. For the electron-injection layer115, an alkali metal, an alkaline earth metal, or a compound thereof,such as lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride(CaF₂), or lithium oxide (LiO_(x)) can be used. A rare earth metalcompound like erbium fluoride (ErF₃) can also be used. An electride mayalso be used for the electron-injection layer 115. Examples of theelectride include a substance in which electrons are added at highconcentration to calcium oxide-aluminum oxide. Any of the substances forforming the electron-transport layer 114, which are given above, can beused.

A composite material in which an organic compound and an electron donor(donor) are mixed may also be used for the electron-injection layer 115.Such a composite material is excellent in an electron-injection propertyand an electron-transport property because electrons are generated inthe organic compound by the electron donor. In this case, the organiccompound is preferably a material that is excellent in transporting thegenerated electrons. Specifically, for example, the substances forforming the electron-transport layer 114 (e.g., a metal complex or aheteroaromatic compound), which are given above, can be used. As theelectron donor, a substance showing an electron-donating property withrespect to the organic compound may be used. Preferable examples are analkali metal, an alkaline earth metal, and a rare earth metal.Specifically, lithium, cesium, magnesium, calcium, erbium, ytterbium,and the like can be used. In addition, an alkali metal oxide or analkaline earth metal oxide is preferable, and lithium oxide, calciumoxide, and barium oxide are given. A Lewis base such as magnesium oxidecan also be used. An organic compound such as tetrathiafulvalene(abbreviation: TTF) can also be used.

Note that each of the above-described hole-injection layer 111,hole-transport layer 112, light-emitting layer 113, electron-transportlayer 114, and electron-injection layer 115 can be formed by a methodsuch as an evaporation method (e.g., a vacuum evaporation method), anink-jet method, or a coating method.

In the above-described light-emitting element, current flows because ofa potential difference applied between the first electrode 101 and thesecond electrode 103 and holes and electrons are recombined in the ELlayer 102, whereby light is emitted. Then, the emitted light isextracted outside through one or both of the first electrode 101 and thesecond electrode 103. Thus, one or both of the first electrode 101 andthe second electrode 103 are electrodes having light-transmittingproperties.

Note that the light-emitting element described in this embodiment is anexample of a light-emitting element in which the organometallic complexobtained by the synthesis method of one embodiment of the presentinvention is used as an EL material. As a light-emitting deviceincluding the above-described light-emitting element, a passive matrixlight-emitting device and an active matrix light-emitting device can befabricated. It is also possible to fabricate a light-emitting deviceincluding a light-emitting element having a microcavity structure. Eachof the light-emitting devices is one embodiment of the presentinvention.

The active-matrix type light-emitting device is explained in Embodiment4.

Note that the structure described in this embodiment can be combined asappropriate with any of the structures described in the otherembodiments.

Embodiment 3

Described in this embodiment is a case of fabricating a light-emittingelement (hereinafter, a tandem light-emitting element) that has astructure in which a charge-generation layer is provided between aplurality of EL layers and the organometallic complex obtained by thesynthesis method of one embodiment of the present invention is used asan EL material in the EL layers.

A light-emitting element described in this embodiment is a tandemlight-emitting element including a plurality of EL layers (a first ELlayer 202(1) and a second EL layer 202(2)) between a pair of electrodes(a first electrode 201 and a second electrode 204) as illustrated inFIG. 2A.

In this embodiment, the first electrode 201 functions as an anode, andthe second electrode 204 functions as a cathode. Note that the firstelectrode 201 and the second electrode 204 can have structures similarto those described in Embodiment 2. In addition, all or any of theplurality of EL layers (the first EL layer 202(1) and the second ELlayer 202(2)) may have structures similar to those described inEmbodiment 2. In other words, the structures of the first EL layer202(1) and the second EL layer 202(2) may be the same or different fromeach other and can be similar to those of the EL layers described inEmbodiment 2.

A charge-generation layer 205 is provided between the plurality of ELlayers (the first EL layer 202(1) and the second EL layer 202(2)). Thecharge-generation layer 205 has a function of injecting electrons intoone of the EL layers and injecting holes into the other of the EL layerswhen voltage is applied between the first electrode 201 and the secondelectrode 204. In this embodiment, when voltage is applied such that thepotential of the first electrode 201 is higher than that of the secondelectrode 204, the charge-generation layer 205 injects electrons intothe first EL layer 202(1) and injects holes into the second EL layer202(2).

Note that in terms of light extraction efficiency, the charge-generationlayer 205 preferably has a property of transmitting visible light(specifically, the charge-generation layer 205 has a visible lighttransmittance of 40% or more). The charge-generation layer 205 functionseven when it has lower conductivity than the first electrode 201 or thesecond electrode 204.

The charge-generation layer 205 may have either a structure in which anelectron acceptor (acceptor) is added to an organic compound having ahigh hole-transport property or a structure in which an electron donor(donor) is added to an organic compound having a high electron-transportproperty. Alternatively, both of these structures may be stacked.

In the case of the structure in which an electron acceptor is added toan organic compound having a high hole-transport property, as theorganic compound having a high hole-transport property, for example, anaromatic amine compound such as NPB, TPD, TDATA, MTDATA, or4,4′-bis[N-(spiro-9,9′-bifluoren-2-yl)-N-phenylamino]biphenyl(abbreviation: BSPB), or the like can be used. The substances listedhere are mainly ones that have a hole mobility of 10⁻⁶ cm²/Vs or higher.Note that any organic compound other than the compounds listed here maybe used as long as the hole-transport property is higher than theelectron-transport property.

As the electron acceptor,7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation:F₄TCNQ), chloranil, and the like can be given. Oxides of metalsbelonging to Groups 4 to 8 of the periodic table can also be given.Specifically, vanadium oxide, niobium oxide, tantalum oxide, chromiumoxide, molybdenum oxide, tungsten oxide, manganese oxide, and rheniumoxide are preferable because of their high electron-acceptingproperties. Among these, molybdenum oxide is especially preferablebecause it is stable in the air, has a low hygroscopic property, and iseasy to handle.

On the other hand, in the case of the structure in which an electrondonor is added to an organic compound having a high electron-transportproperty, as the organic compound having a high electron-transportproperty, for example, a metal complex having a quinoline skeleton or abenzoquinoline skeleton, such as Alq, Almq₃, BeBq₂, or BAlq, or the likecan be used. Alternatively, a metal complex having an oxazole-basedligand or a thiazole-based ligand, such as ZnPBO or ZnBTZ can be used.Alternatively, in addition to such a metal complex, PBD, OXD-7, TAZ,Bphen, BCP, or the like can be used. The substances listed here aremainly ones that have an electron mobility of 10⁻⁶ cm²/Vs or higher.Note that any organic compound other than the compounds listed here maybe used as long as the electron-transport property is higher than thehole-transport property.

As the electron donor, it is possible to use an alkali metal, a rareearth metal, metals belonging to Groups 2, 3 and 13 of the periodictable, or an oxide or carbonate thereof. Specifically, lithium (Li),cesium (Cs), magnesium (Mg), calcium (Ca), ytterbium (Yb), indium (In),lithium oxide, cesium carbonate, or the like is preferably used.Alternatively, an organic compound such as tetrathianaphthacene may beused as the electron donor.

Although the light-emitting element including two EL layers is describedin this embodiment, the present invention can be similarly applied to alight-emitting element in which n EL layers (202(1) to 202(n)) (n isthree or more) are stacked as illustrated in FIG. 2B. In the case wherea plurality of EL layers are included between a pair of electrodes as inthe light-emitting element according to this embodiment, by providingcharge-generation layers (205(1) to 205(n−1)) between the EL layers,light emission in a high luminance region can be obtained with currentdensity kept low. Since the current density can be kept low, the elementcan have a long lifetime.

When the EL layers have different emission colors, a desired emissioncolor can be obtained from the whole light-emitting element. Forexample, in the light-emitting element having two EL layers, when anemission color of the first EL layer and an emission color of the secondEL layer are made to be complementary colors, a light-emitting elementemitting white light as a whole light-emitting element can also beobtained. Note that “complementary colors” refer to colors that canproduce an achromatic color when mixed. In other words, emission ofwhite light can be obtained by mixture of light emitted from substanceswhose emission colors are complementary colors.

The same can be applied to a light-emitting element having three ELlayers. For example, the light-emitting element as a whole can providewhite light emission when the emission color of the first EL layer isred, the emission color of the second EL layer is green, and theemission color of the third EL layer is blue.

Note that the structure described in this embodiment can be combined asappropriate with any of the structures described in the otherembodiments.

Embodiment 4

Described in this embodiment is a light-emitting device that includes alight-emitting element in which the organometallic complex obtained bythe synthesis method of one embodiment of the present invention is usedas an EL material in a light-emitting layer.

The light-emitting device may be either a passive matrix typelight-emitting device or an active matrix type light-emitting device.Note that any of the light-emitting elements described in the otherembodiments can be used for the light-emitting device described in thisembodiment.

In this embodiment, an active matrix light-emitting device is describedwith reference to FIGS. 3A and 3B.

Note that FIG. 3A is a top view illustrating a light-emitting device andFIG. 3B is a cross-sectional view taken along the chain line A-A′ inFIG. 3A. The active matrix light-emitting device according to thisembodiment includes a pixel portion 302 provided over an elementsubstrate 301, a driver circuit portion (a source line driver circuit)303, and driver circuit portions (gate line driver circuits) 304 a and304 b. The pixel portion 302, the driver circuit portion 303, and thedriver circuit portions 304 a and 304 b are sealed between the elementsubstrate 301 and a sealing substrate 306 with a sealant 305.

Over the element substrate 301, a lead wiring 307 for connecting anexternal input terminal, through which a signal (e.g., a video signal, aclock signal, a start signal, a reset signal, or the like) or electricpotential from the outside is transmitted to the driver circuit portion303 and the driver circuit portions 304 a and 304 b, is provided. Here,an example is described in which a flexible printed circuit (FPC) 308 isprovided as the external input terminal. Although only the FPC isillustrated here, the FPC may be provided with a printed wiring board(PWB). The light-emitting device in this specification includes, in itscategory, not only the light-emitting device itself but also thelight-emitting device provided with the FPC or the PWB.

Next, a cross-sectional structure is described with reference to FIG.3B. The driver circuit portion and the pixel portion are formed over theelement substrate 301; the driver circuit portion 303 that is the sourceline driver circuit and the pixel portion 302 are illustrated here.

The driver circuit portion 303 is an example in which an FET 309 and anFET 310 are combined. Note that the driver circuit portion 303 may beformed with a circuit including transistors having the same conductivitytype (either an n-channel transistor or a p-channel transistor) or aCMOS circuit including an n-channel transistor and a p-channeltransistor. Although this embodiment shows a driver integrated type inwhich the driver circuit is formed over the substrate, the drivercircuit is not necessarily formed over the substrate, and may be formedoutside the substrate.

The pixel portion 302 includes a plurality of pixels each of whichincludes a switching FET 311, a current control FET 312, and a firstelectrode (anode) 313 that is electrically connected to a wiring (asource electrode or a drain electrode) of the current control FET 312.Although the pixel portion 302 includes two FETs, the switching FET 311and the current control FET 312, in this embodiment, one embodiment ofthe present invention is not limited thereto. The pixel portion 302 mayinclude, for example, three or more FETs and a capacitor in combination.

As the FETs 309, 310, 311, and 312, for example, a staggered transistoror an inverted staggered transistor can be used. Examples of asemiconductor material that can be used for the FETs 309, 310, 311, and312 include Group IV semiconductors (e.g., silicon), Group IIsemiconductors (e.g., gallium), compound semiconductors, oxidesemiconductors, and organic semiconductors. There is no particularlimitation on the crystallinity of the semiconductor material, and anamorphous semiconductor or a crystalline semiconductor can be used. Anoxide semiconductor is preferably used for the FETs 309, 310, 311, and312. Examples of the oxide semiconductor include an In—Ga oxide and anIn-M-Zn oxide (M is Al, Ga, Y, Zr, La, Ce, or Nd). For example, an oxidesemiconductor that has an energy gap of 2 eV or more, preferably 2.5 eVor more, further preferably 3 eV or more is used for the FETs 309, 310,311, and 312, so that the off-state current of the transistors can bereduced.

An insulator 314 is formed to cover end portions of the first electrode313. In this embodiment, the insulator 314 is formed using a positivephotosensitive acrylic resin. The first electrode 313 is used as ananode in this embodiment.

The insulator 314 preferably has a curved surface with curvature at anupper end portion or a lower end portion thereof. This enables thefavorable coverage with a film to be formed over the insulator 314. Theinsulator 314 can be formed using, for example, either a negativephotosensitive resin or a positive photosensitive resin. The material ofthe insulator 314 is not limited to an organic compound and an inorganiccompound such as silicon oxide, silicon oxynitride, or silicon nitridecan also be used.

An EL layer 315 and a second electrode (cathode) 316 are stacked overthe first electrode (anode) 313. In the EL layer 315, at least alight-emitting layer is provided. In the EL layer 315, a hole-injectionlayer, a hole-transport layer, an electron-transport layer, anelectron-injection layer, a charge-generation layer, and the like can beprovided as appropriate in addition to the light-emitting layer.

A light-emitting element 317 is formed of a stack of the first electrode(anode) 313, the EL layer 315, and the second electrode (cathode) 316.For the first electrode (anode) 313, the EL layer 315, and the secondelectrode (cathode) 316, any of the materials given in Embodiment 2 canbe used. Although not illustrated, the second electrode (cathode) 316 iselectrically connected to the FPC 308 which is an external inputterminal.

Although the cross-sectional view of FIG. 3B illustrates only onelight-emitting element 317, a plurality of light-emitting elements arearranged in matrix in the pixel portion 302. Light-emitting elementsthat emit light of three kinds of colors (R, G, and B) are selectivelyformed in the pixel portion 302, whereby a light-emitting device capableof full color display can be obtained. In addition to the light-emittingelements that emit light of three kinds of colors (R, G, and B), forexample, light-emitting elements that emit light of white (W), yellow(Y), magenta (M), cyan (C), and the like may be formed. For example, thelight-emitting elements that emit light of a plurality of kinds ofcolors are used in combination with the light-emitting elements thatemit light of three kinds of colors (R, G, and B), whereby color purityand a reduction in power consumption can be improved. Alternatively, alight-emitting device that is capable of full color display may befabricated by combination with color filters.

The sealing substrate 306 is attached to the element substrate 301 withthe sealant 305, whereby a light-emitting element 317 is provided in aspace 318 surrounded by the element substrate 301, the sealing substrate306, and the sealant 305. Note that the space 318 may be filled with aninert gas (such as nitrogen and argon) or the sealant 305.

An epoxy-based resin or glass frit is preferably used for the sealant305. The material preferably allows as little moisture and oxygen aspossible to penetrate. As the sealing substrate 306, a glass substrate,a quartz substrate, or a plastic substrate formed of fiber-reinforcedplastic (FRP), poly(vinyl fluoride) (PVF), a polyester, an acrylicresin, or the like can be used. In the case where glass frit is used asthe sealant, the element substrate 301 and the sealing substrate 306 arepreferably glass substrates for high adhesion.

As described above, an active matrix light-emitting device can beobtained.

Note that the structure described in this embodiment can be combined asappropriate with any of the structures described in the otherembodiments.

Embodiment 5

In this embodiment, examples of an electronic device manufactured usinga light-emitting device in which the organometallic complex obtained bythe synthesis method of one embodiment of the present invention is usedas an EL material are described with reference to FIGS. 4A to 4D.

Examples of electronic devices including the light-emitting deviceinclude television devices (also referred to as TV or televisionreceivers), monitors for computers and the like, cameras such as digitalcameras and digital video cameras, digital photo frames, mobile phones(also referred to as portable telephone devices), portable gamemachines, portable information terminals, audio playback devices, andstationary game machines such as pachinko machines. Specific examples ofthe electronic devices are illustrated in FIGS. 4A to 4D.

FIG. 4A illustrates an example of a television device. In the televisiondevice 7100, a display portion 7103 is incorporated in a housing 7101.Images can be displayed by the display portion 7103, and thelight-emitting device can be used for the display portion 7103. Here,the housing 7101 is supported by a stand 7105.

The television device 7100 can be operated by an operation switch of thehousing 7101 or a separate remote controller 7110. With operation keys7109 of the remote controller 7110, channels and volume can becontrolled and images displayed on the display portion 7103 can becontrolled. Furthermore, the remote controller 7110 may be provided witha display portion 7107 for displaying data output from the remotecontroller 7110.

Note that the television device 7100 is provided with a receiver, amodem, and the like. With the use of the receiver, general televisionbroadcasts can be received. Moreover, when the television device isconnected to a communication network with or without wires via themodem, one-way (from a sender to a receiver) or two-way (between asender and a receiver or between receivers) information communicationcan be performed.

FIG. 4B illustrates a computer, which includes a main body 7201, ahousing 7202, a display portion 7203, a keyboard 7204, an externalconnection port 7205, a pointing device 7206, and the like. Note thatthis computer can be manufactured using the light-emitting device forthe display portion 7203.

FIG. 4C illustrates a smart watch, which includes a housing 7302, adisplay panel 7304, operation buttons 7311 and 7312, a connectionterminal 7313, a band 7321, a clasp 7322, and the like.

The display panel 7304 mounted in the housing 7302 serving as a bezelincludes a non-rectangular display region. The display panel 7304 candisplay an icon 7305 indicating time, another icon 7306, and the like.

The smart watch illustrated in FIG. 4C has a variety of functions, forexample, a function of displaying a variety of information (e.g., astill image, a moving image; and a text image) on a display portion, atouch panel function, a function of controlling processing with avariety of software (programs), a wireless communication function, and afunction of storing data.

The housing 7302 can include a speaker, a sensor (a sensor having afunction of measuring or sensing force, displacement, position, speed,acceleration, angular velocity, rotational frequency, distance, light,liquid, magnetism, temperature, chemical substance, sound, hardness,electric field, current, voltage, electric power, radiation, humidity,gradient, oscillation, odor, or infrared rays), a microphone, and thelike. Note that the smart watch can be manufactured using thelight-emitting device for the display panel 7304.

FIG. 4D illustrates an example of a mobile phone. A mobile phone 7400includes a housing 7401 provided with a display portion 7402, amicrophone 7406, a speaker 7405, a camera 7407, an external connectionportion 7404, an operation button 7403, and the like. In the case wherethe light-emitting element of one embodiment of the present invention isformed over a flexible substrate, the light-emitting element can be usedfor the display portion 7402 having a curved surface as illustrated inFIG. 4D.

When the display portion 7402 of the mobile phone 7400 illustrated inFIG. 4D is touched with a finger or the like, data can be input to themobile phone 7400. Operations such as making a call and composing e-mailcan be performed by touch on the display portion 7402 with a finger orthe like.

There are mainly three screen modes of the display portion 7402. Thefirst mode is a display mode mainly for displaying an image. The secondmode is an input mode mainly for inputting data such as characters. Thethird mode is a display-and-input mode in which two modes of the displaymode and the input mode are combined.

For example, in the case of making a call or composing e-mail, acharacter input mode mainly for inputting characters is selected for thedisplay portion 7402 so that characters displayed on the screen can beinput. In this case, it is preferable to display a keyboard or numberbuttons on almost the entire screen of the display portion 7402.

When a detection device such as a gyro sensor or an acceleration sensoris provided inside the mobile phone 7400, display on the screen of thedisplay portion 7402 can be automatically changed by determining theorientation of the mobile phone 7400 (whether the mobile phone is placedhorizontally or vertically).

The screen modes are changed by touch on the display portion 7402 oroperation with the button 7403 of the housing 7401. The screen modes canbe switched depending on the kind of images displayed on the displayportion 7402. For example, when a signal of an image displayed on thedisplay portion is a signal of moving image data, the screen mode isswitched to the display mode. When the signal is a signal of text data,the screen mode is switched to the input mode.

In the input mode, when it is determined that input by touch on thedisplay portion 7402 is not performed within a specified period on thebasis of a signal detected by an optical sensor in the display portion7402, the screen mode may be controlled so as to be switched from theinput mode to the display mode.

The display portion 7402 may function as an image sensor. For example,an image of a palm print, a fingerprint, or the like is taken by touchon the display portion 7402 with the palm or the finger, wherebypersonal authentication can be performed. When a sensing light sourcethat emits near-infrared light is provided in the display portion, animage of a finger vein, a palm vein, or the like can be taken.

As described above, the electronic devices can be obtained using thelight-emitting device that includes the light-emitting element of oneembodiment of the present invention. Note that the light-emitting devicecan be used for electronic devices in a variety of fields without beinglimited to the electronic devices described in this embodiment.

Note that the structure described in this embodiment can be combined asappropriate with any of the structures described in the otherembodiments.

Embodiment 6

In this embodiment, examples of a lighting device that includes alight-emitting device containing the organometallic complex obtained bythe synthesis method of one embodiment of the present invention aredescribed with reference to FIG. 5.

FIG. 5 illustrates an example in which the light-emitting device is usedas an indoor lighting device 8001. Since the light-emitting device canhave a large area, it can be used for a lighting device having a largearea. A lighting device 8002 in which a light-emitting region has acurved surface can also be obtained with the use of a housing with acurved surface. A light-emitting element included in the light-emittingdevice described in this embodiment can be in a thin film form, whichallows the housing to be designed more freely. Thus, the lighting devicecan be elaborately designed in a variety of ways. A wall of the room maybe provided with a large-sized lighting device 8003.

When the light-emitting device is used at a surface of a table, alighting device 8004 that has a function as a table can be obtained.When the light-emitting device is used as part of other furniture, alighting device that functions as the furniture can be obtained.

As described above, a variety of lighting devices that include thelight-emitting device can be obtained. Note that these lighting devicesare also embodiments of the present invention.

Note that the structure described in this embodiment can be combined asappropriate with any of the structures described in the otherembodiments.

Example 1 Synthesis Example 1

Described in this example is a synthetic method according to anembodiment of the present invention, leading to an organometalliccomplex,bis{4,6-dimethyl-2-[5-(2,6-dimethylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κN]phenyl-κC}(2,8-dimethyl-4,6-nonanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dmdppr-dmp)₂(divm)]), represented by StructuralFormula (300). The structure of [Ir(dmdppr-dmp)₂(divm)] is shown below.

Step 1: Synthesis of 5,6-bis(3,5-dimethylphenyl)pyrazin-2-ol

First, 5.33 g (20 mmol) of 3,3′,5,5′-tetramethylbenzil, 2.65 g (24 mmol)of glycinamide hydrochloride, 1.92 g (48 mmol) of sodium hydroxide, and50 mL of methanol were put into a 1-L three-neck flask, and the air inthe flask was replaced with nitrogen. This mixture was heated for refluxfor approximately 3 hours.

Then, the temperature of the flask was returned to room temperature, 2.5mL of 12 M concentrated hydrochloric acid was added to this mixture, andstirring was performed for approximately 30 minutes. After that, 2 g ofpotassium bicarbonate and 25 mL of water were added. Filtration wasperformed to give a solid and the solid was washed with water andmethanol in this order. The resulting residue was dried at 100° C. underreduced pressure and recrystallized with 50 mL of toluene to give 4.83 gof a yellow solid, which was an objective substance, in a yield of 79%.

The synthesis scheme of Step 1 is shown in (a-1).

Step 2: Synthesis of 5,6-bis(3,5-dimethylphenyl)-2-pyrazyl triflate

Into a 200-mL three-neck flask was put 3.96 g (13 mmol) of5,6-bis(3,5-dimethylphenyl)pyrazin-2-ol obtained in Step 1, and the airin the flask was replaced with nitrogen. Then, 65 mL of dichloromethane(abbreviation: DCM) and 3.6 mL of triethylamine (abbreviation: NEt₃)were added under a nitrogen atmosphere. Then, to this solution, 2.8 mL(16.9 mmol) of trifluoromethanesulfonic anhydride (abbreviation: Tf₂O)was added dropwise at 0° C., and the mixture was stirred at 0° C. for 30minutes and at room temperature for 12 hours.

The flask was cooled again with ice, 30 mL of water was added, and themixture was separated into an organic layer and an aqueous layer. Theaqueous layer was subjected to extraction with dichloromethane. Theorganic layer and the extract solution were combined, washed with 1 Mhydrochloric acid and then a saturated aqueous solution of sodiumbicarbonate, added with magnesium sulfate, and subjected to gravityfiltration. The solvent in the filtrate was distilled off, andpurification was conducted by column chromatography using a mixedsolvent of hexane, ethyl acetate, and toluene as a mobile phase; thus,5.7 g of a yellow-brown oily substance, which was an objectivesubstance, was obtained in a yield of 99%.

The synthesis scheme of Step 2 is shown in (a-2).

Results of analysis of the yellow-brown oily substance obtained in Step2 by nuclear magnetic resonance spectrometry (¹H-NMR) are shown below. A¹H-NMR chart is shown in FIG. 6. These results show that5,6-bis(3,5-dimethylphenyl)-2-pyrazyl triflate that is one embodiment ofthe present invention was synthesized in Step 2.

¹H NMR (CDCl₃, 500 MHz): δ (ppm)=2.23 (s, 6H), 2.25 (s, 6H), 7.00 (d,J=5.5 Hz, 2H), 7.06 (d, J=6 Hz, 4H), 8.51 (s, 1H).

Step 3: Synthesis of5-(2,6-dimethylphenyl)-2,3-bis(3,5-dimethylphenyl)pyrazine(abbreviation: Hdmdppr-dmp)

Next, 2.18 g (5.0 mmol) of 5,6-bis(3,5-dimethylphenyl)-2-pyrazyltriflate obtained in Step 2, 0.90 g (6.0 mmol) of2,6-dimethylphenylboronic acid, 3.82 g (18 mmol) of tripotassiumphosphate, 37 mL of toluene, and 4 mL of water were put into a 200-mLthree-neck flask, degassing was performed under reduced pressure, andthen the air in the flask was replaced with nitrogen. Then, 46 mg (0.05mmol) of tris(dibenzylideneacetone)dipalladium(0) (abbreviation:Pd₂(dba)₃) and 88 mg (0.20 mmol) of tris(2,6-dimethoxyphenyl)phosphinewere added, and the mixture was heated for reflux for 2 hours.

Water and toluene were added to the mixture, and the resulting mixturewas separated into an organic layer and an aqueous layer. The aqueouslayer was subjected to extraction with toluene. The organic layer andthe extract solution were combined, the mixture was washed with water,and then the solvent was distilled off. The resulting residue waspurified by column chromatography using a mixed solvent of hexane, ethylacetate, and toluene as a mobile phase, so that 1.96 g of Hdmdppr-dmp,which was an objective substance, was obtained as a yellowish whitesolid in a yield of 99%.

The synthesis scheme of Step 3 is shown in (a-3).

Results of analysis of the yellowish white solid obtained in Step 3 by¹H-NMR are shown below. A ¹H-NMR chart is shown in FIG. 7. These resultsshow that Hdmdppr-dmp, which was a 2,3,5-triarylpyrazine derivative ofone embodiment of the present invention, was synthesized in Step 3.

¹H NMR (CDCl₃, 500 MHz): δ (ppm)=2.19 (s, 6H), 2.23 (s, 6H), 2.26 (s,6H), 6.96 (d, J=15 Hz, 2H), 7.10 (s, 2H), 7.12-7.18 (m, 4H), 7.22-7.27(m, 1H), 8.51 (s, 1H).

Step 4: Synthesis ofdi-μ-chloro-tetrakis{4,6-dimethyl-2-[5-(2,6-dimethylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κN]phenyl-κC}diiridium(III)(abbreviation: [Ir(dmdppr-dmp)₂Cl]₂)

Next, 1.77 g (4.5 mmol) of Hdmdppr-dmp obtained in Step 3, 0.71 g (2.25mmol) of iridium(III) chloride hydrate, 45 mL of 2-ethoxyethanol, and 15mL of water were put into a round-bottom flask. The mixture was bubbledwith argon for approximately 10 minutes to replace the air in the flaskwith argon, and heating by irradiation with microwaves (2.45 GHz, 100 W)was performed for 2 hours. Note that in the specification, theirradiation with microwaves was performed using a microwave synthesissystem (Discover, manufactured by CEM Corporation).

The solvent in the obtained mixture was distilled off, the residue wassuspended in ethanol and filtered, and the resulting solid was washedwith ethanol. The resulting solid was dried at 100° C. under reducedpressure, so that 1.84 g of a dinuclear complex [Ir(dmdppr-dmp)₂Cl]₂,which was an objective substance, was obtained as a red solid in a yieldof 81%.

The synthesis scheme of Step 4 is shown in (a-4).

Step 5: Synthesis of [Ir(dmdppr-dmp)₂(divm)]

Then, 1.72 g of [Ir(dmdppr-dmp)₂Cl]₂ obtained in Step 4, 0.47 g of2,8-dimethyl-4,6-nonanedione (abbreviation: Hdivm), 0.90 g of sodiumcarbonate, and 9 mL of 2-ethoxyethanol were put into a round-bottomflask, and the mixture was bubbled with argon for approximately 10minutes to replace the air in the flask with argon. After that,irradiation with microwaves (2.45 GHz, 120 W) was performed for 2 hours.The solvent was distilled off from the obtained mixture, and theresulting residue was suspended in methanol, filtered, and washed withwater and methanol.

The obtained solid was dissolved in dichloromethane, and filteredthrough a filter aid in which Celite, alumina, and Celite were stackedin this order. The solvent in the filtrate was distilled off,recrystallization was performed using dichloromethane and methanol, andthe resulting solid was dried by heating at 100° C. under reducedpressure, so that 1.42 g of the organometallic complex[Ir(dmdppr-dmp)₂(divm)] was obtained as a dark red powder in a yield of72%.

The synthesis scheme of Step 5 is shown in (a-5) below.

Results of analysis of the dark red powder obtained in Step 5 by ¹H-NMRare shown below. A ¹H-NMR chart is shown in FIG. 8. These results showthat an organometallic complex [Ir(dmdppr-dmp)₂(divm)](StructuralFormula (300)) was synthesized in Step 5.

¹H NMR (CDCl₃, 500 MHz): δ (ppm)=0.56-0.63 (dd, 121H), 1.79-1.84 (m,2H), 1.92 (s, 4H), 2.22 (s, 12H), 5.19 (s, 1H), 6.46-6.47 (d, 2H),6.52-6.55 (dt, 2H), 6.65-6.68 (t, 2H), 6.93-6.95 (d, 2H), 7.12-7.14 (d,4H), 7.20-7.22 (d, 2H), 7.51 (s, 6H), 7.73 (s, 4H), 8.48 (s, 2H).

Example 2 Synthesis Example 2

Described in this example is a synthetic method according to anembodiment of the present invention, leading to an organometalliccomplex,bis[2-(3,5-diphenyl-2-pyrazinyl-κN)-phenyl-κC](2,2,6,6-tetramethyl-3,5-heptanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(tppr)₂(dpm)]), represented by Structural Formula(310). The structure of [Ir(tppr(dpm)] is shown below.

Step 1: Synthesis of 5,6-diphenylpyrazin-2-ol

First, 21.0 g (100 mmol) of benzil, 13.3 g (120 mmol) of glycinamidehydrochloride, 9.6 g (240 mmol) of sodium hydroxide, and 500 mL ofmethanol were put into a 1-L three-neck flask, and the air in the flaskwas replaced with nitrogen. This mixture was heated for reflux forapproximately 3 hours.

Then, the temperature of the flask was returned to room temperature,12.5 mL of 12 M concentrated hydrochloric acid was added to thismixture, and stirring was performed for approximately 30 minutes. Then,10 g of potassium bicarbonate and 125 mL of water were added. Filtrationwas performed to give a solid, and the solid was washed with water andmethanol in this order. The resulting residue was dried at 100° C. underreduced pressure and recrystallized with 50 mL of toluene to give 19.5 gof a yellow solid, which was an objective substance, in a yield of 79%.

The synthesis scheme of Step 1 is shown in (b-1).

Step 2: Synthesis of 5,6-diphenyl-2-pyrazyl triflate

Into a 2-L three-neck flask was put 18.6 g (75 mmol) of5,6-diphenylpyrazin-2-ol obtained in Step 1, and the air in the flaskwas replaced with nitrogen. Then, 750 mL of dichloromethane and 21 mL oftriethylamine were added under a nitrogen atmosphere, 16.4 mL (97.5mmol) of trifluoromethanesulfonic anhydride was added dropwise to thissolution at 0° C., and the mixture was stirred at 0° C. for 30 minutesand at room temperature for 12 hours.

The flask was cooled again with ice, 250 mL of water was added, and themixture was separated into an organic layer and an aqueous layer. Theaqueous layer was subjected to extraction with dichloromethane. Theorganic layer and the extract solution were combined, washed with 1 Mhydrochloric acid and then a saturated aqueous solution of sodiumbicarbonate, added with magnesium sulfate, and subjected to gravityfiltration. The solvent in the filtrate was distilled off, and theobtained residue was purified by column chromatography using a mixedsolvent of hexane, ethyl acetate, and toluene as a mobile phase; thus,27.8 g of a yellow-brown oily substance, which was an objectivesubstance, was obtained in a yield of 97%.

The synthesis scheme of Step 2 is shown in (b-2).

Results of analysis of the yellow-brown oily substance obtained in Step2 by ¹H-NMR are shown below. A ¹H-NMR chart is shown in FIG. 9. Theseresults show that 5,6-diphenyl-2-pyrazyl triflate that is one embodimentof the present invention was synthesized in Step 2.

¹H NMR (CDCl₃, 500 MHz): δ (ppm)=7.28-7.41 (m, 6H), 7.42-7.48 (m, 4H),8.56 (s, 1H).

Step 3: Synthesis of 2,3,5-triphenylpyrazine (abbreviation: Htppr)

Next, 13.3 g (35 mmol) of 5,6-diphenyl-2-pyrazyl triflate obtained inStep 2, 5.12 g (42 mmol) of phenylboronic acid, 26.8 g (126 mmol) oftripotassium phosphate, 260 mL of toluene, and 26 mL of water were putinto a 500-mL three-neck flask, degassing was performed under reducedpressure, and then the air in the flask was replaced with nitrogen.Then, 321 mg (0.35 mmol) of tris(dibenzylideneacetone)dipalladium(0)(abbreviation: Pd₂(dba)₃) and 619 mg (1.40 mmol) oftris(2,6-dimethoxyphenyl)phosphine were added, and the mixture washeated for reflux for 2 hours.

Water and toluene were added to the mixture, and the resulting mixturewas separated into an organic layer and an aqueous layer. The aqueouslayer was subjected to extraction with toluene. The organic layer andthe extract solution were combined, the mixture was washed with water,and then the solvent was distilled off. The resulting residue waspurified by column chromatography using a mixed solvent of hexane, ethylacetate, and toluene as a mobile phase, so that 10.0 g of Htppr, whichwas an objective substance, was obtained as a yellowish white solid in ayield of 93%.

The synthesis scheme of Step 3 is shown in (b-3).

Results of analysis of the yellowish white solid obtained in Step 3 by¹H-NMR are shown below. A ¹H-NMR chart is shown in FIG. 10. Theseresults show that Htppr, which was a 2,3,5-triarylpyrazine derivative ofone embodiment of the present invention, was synthesized in Step 3.

¹H NMR (CDCl₃, 500 MHz): δ (ppm)=7.28-7.38 (m, 6H), 7.46-7.59 (m, 7H),8.17 (d, J=7.5 Hz, 2H), 9.04 (s, 1H).

Step 4: Synthesis ofdi-μ-chloro-tetrakis[2-(3,5-diphenyl-2-pyrazinyl-κN)phenyl-κC]diiridium(III)(abbreviation: [Ir(tppr)₂Cl]₂)

Next, 9.25 g (30 mmol) of Htppr obtained in Step 3, 4.75 g (15 mmol) ofiridium(m) chloride hydrate, 300 mL of 2-ethoxyethanol, and 100 mL ofwater were put into a 1-L three-neck flask. The mixture was bubbled withargon for approximately 10 minutes to replace the air in the flask withargon, and heating by irradiation with microwaves (2.45 GHz, 400 W) wasperformed for 3 hours.

The obtained mixture was filtered, and the residue was washed withethanol. The resulting solid was dried at 100° C. under reducedpressure, so that 10.3 g of a dinuclear complex [Ir(tppr)₂Cl]₂, whichwas an objective substance, was obtained as a red solid in a yield of82%.

The synthesis scheme of Step 4 is shown in (b-4).

Step 5: Synthesis of [Ir(tppr)₂(dpm)]

Then, 10.1 g of [Ir(tppr)₂Cl]₂ obtained in Step 4, 3.32 g of2,2,6,6-tetramethyl-3,5-heptanedione (abbreviation: Hdpm), 6.36 g ofsodium carbonate, and 60 mL of 2-ethoxyethanol were put into a 300-mLthree-neck flask, and the mixture was bubbled with argon forapproximately 10 minutes to replace the air in the flask with argon.After that, irradiation with microwaves (2.45 GHz, 400 W) was performedfor 1 hour. The obtained mixture was filtered, and the resulting solidwas washed with ethanol, water, and ethanol in this order.

The obtained solid was dissolved in dichloromethane, and filteredthrough a filter aid in which Celite, alumina, and Celite were stackedin this order. The solvent in the filtrate was distilled off,recrystallization was performed using dichloromethane and methanol, andthe resulting solid was dried by being heated at 100° C. under reducedpressure, so that 11.1 g of the organometallic complex [Ir(tppr)₂(dpm)]was obtained as a dark red powder in a yield of 93%.

The synthesis scheme of Step 5 is shown in (b-5) below.

Results of analysis of the dark red powder obtained in Step 5 by ¹H-NMRare shown below. A ¹H-NMR chart is shown in FIG. 11. These results showthat an organometallic complex [Ir(tppr)₂(dpm)](Structural Formula(310)) was synthesized in Step 5.

¹H NMR (CDC₃, 500 MHz): δ (ppm)=1.02 (s, 18H), 5.63 (s, 1H), 6.51 (t,J=7.5 Hz, 4H), 6.64 (t, J=7.5 Hz, 2H), 6.92 (d, J=8.0 Hz, 2H), 7.42-7.53(m, 6H), 7.54-7.59 (br, 6H), 7.76-7.85 (br, 4H), 8.07 (d, J=6.5 Hz, 4H),8.86 (s, 2H).

Example 3 Synthesis Example 3

Described in this example is a synthetic method according to anembodiment of the present invention, leading to an organometalliccomplex,bis{2-[5-(2,6-dimethylphenyl)-3-phenyl-2-pyrazinyl-κN]-phenyl-κC}(2,8-dimethyl-4,6-nonanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dppr-dmp)₂(divm)]), represented by Structural Formula(312). The structure of [Ir(dppr-dmp)₂(divm)] is shown below.

Step 1: Synthesis of 5,6-diphenylpyrazin-2-ol

First, 4.2 g (20 mmol) of benzil, 2.21 g (20 mmol) of glycinamidehydrochloride, and 40 mL of methanol were put into a three-neck flaskequipped with a reflux pipe, the air in the flask was replaced withnitrogen, the mixture was refluxed, an aqueous solution of 1.6 g (40mmol) of sodium hydroxide in 3.2 mL of water was added, and the refluxwas continued for 3 hours. Then, stirring was performed until thetemperature of the flask was returned to room temperature. After that,2.5 mL of 12M concentrated hydrochloric acid, 2 g of potassiumbicarbonate, and 25 mL of water were added to this mixture, andfiltration was performed.

The obtained residue was dried at 100° C. under reduced pressure andpurified by silica gel column chromatography using chloroform and ethylacetate in a 5:2 ratio as a developing solvent. The solvent in thesolution was distilled off and the resulting residue was recrystallizedwith hexane; thus, 3.04 g of a yellow solid, which was an objectivesubstance, was obtained in a yield of 89%.

The synthesis scheme of Step 1 is shown in (c-1) below.

Step 2: Synthesis of 5,6-diphenyl-2-pyrazyl triflate

Into a three-neck flask were put 2.48 g (10 mmol) of5,6-diphenylpyrazin-2-ol obtained in Step 1, 100 mL of dichloromethane,and 2.8 mL of triethylamine. The air in the flask was replaced withnitrogen, and 2.4 mL of trifluoromethanesulfonic anhydride was addeddropwise at 0° C. The mixture was stirred at 0° C. for 1.5 hours and atroom temperature for 12 hours.

After the reaction, while the flask was cooled with ice, 30 mL of waterwas added to the mixture, and the organic layer was extracted withdichloromethane. The extract was washed with a saturated aqueoussolution of sodium bicarbonate. Magnesium sulfate was added and gravityfiltration was performed. The solvent in the filtrate was distilled offand the resulting residue was purified by silica gel columnchromatography using hexane, ethyl acetate, and toluene in a 20:2:10ratio as a developing solvent. Thus, 3.73 g of a yellow-brown oilysubstance, which was an objective substance, was obtained in a yield of98%.

A synthesis scheme of Step 2 is shown in (c-2) below.

The result of the ¹H-NMR analysis of the yellow-brown oily substanceobtained in Step 2 was the same as that obtained in Step 2 of Example 2.That is, 5,6-diphenyl-2-pyrazyl triflate that is one embodiment of thepresent invention was also synthesized in Step 2 of Example 3.

Step 3: Synthesis of 2-(2,6-dimethylphenyl)-5,6-diphenylpyrazine(abbreviation: Hdppr-dmp)

Next, 2.66 g (7.0 mmol) of 5,6-diphenyl-2-pyrazyl triflate obtained inStep 2, 2.10 g (14 mmol) of 2,6-dimethylphenylboronic acid, 2.23 g (21.0mmol) of sodium carbonate, 24 mL of N,N-dimethylformamide (abbreviation:DMF), and 24 mL of water were put into a round-bottom flask equippedwith a reflux pipe, the air in the flask was replaced with nitrogen,49.1 mg (0.07 mmol) of bis(triphenylphosphine)palladium(II) dichloride(abbreviation: PdCl₂(PPh₃)₂) was added, and irradiation with microwaves(2.45 GHz, 100 W) was performed for 2 hours.

To the resulting mixture, 25 mg (0.035 mmol) of PdCl₂(PPh₃)₂ was addedagain, and the mixture was irradiated with microwaves (2.45 GHz, 100 W)for 2 hours. Furthermore, 25 mg (0.035 mmol) of PdCl₂(PPh₃)₂ and 1.1 g(7.0 mmol) of 2,6-dimethylphenylboronic acid were added and irradiationwith microwaves (2.45 GHz, 100 W) was performed for 2 hours. Water wasadded to the resulting mixture, and the organic layer was extracted withtoluene. The extract solution was washed with water, and the solvent wasdistilled off. The resulting residue was purified by silica gel columnchromatography using hexane, ethyl acetate, and toluene in a 20:2:10ratio as a developing solvent, so that Hdppr-dmp, which was an objectivepyrazine derivative, was obtained as a yellowish white solid in a yieldof 38%.

A synthesis scheme of Step 3 is shown in (c-3) below.

Results of analysis of the yellowish white solid obtained in Step 3 by¹H-NMR are shown below. A ¹H-NMR chart is shown in FIG. 12. Theseresults show that Hdppr-dmp, which was a synthetic intermediate and a2,3,5-triarylpyrazine derivative of one embodiment of the presentinvention, was synthesized in Step 3.

¹H NMR (CDCl₃, 500 MHz): δ (ppm)=2.15 (s, 6H), 7.16 (d, 2H), 7.26-7.34(m, 7H), 7.47 (d, 2H), 7.50 (d, 2H), 8.52 (s, 1H).

Step 4: Synthesis ofdi-μ-chloro-tetrakis{2-[5-(2,6-dimethylphenyl)-3-phenyl-2-pyrazinyl-κN]-phenyl-κC}diiridium(III)(abbreviation: [Ir(dppr-dmp)₂Cl]₂)

Next, 0.84 g (2.5 mmol) of Hdppr-dmp obtained in Step 3, 0.38 g (1.2mmol) of iridium(III) chloride hydrate, 30 mL of 2-ethoxyethanol, and 10mL of water were put into a round-bottom flask equipped with a refluxpipe. The air in the flask was replaced with argon, and heating byirradiation with microwaves (2.45 GHz, 100 W) was performed for 2 hours.

The solvent in the resulting mixture was distilled off and the resultingresidue was washed with methanol; thus, 0.46 g of a dinuclear complex[Ir(dppr-dmp)₂Cl]₂, which was an objective substance, was obtained as adark red powder solid in a yield of 41%.

The synthesis scheme of Step 4 is shown in (c-4) below.

Step 5: Synthesis of [Ir(dppr-dmp)₂(divm)]

Then, 0.46 g (0.26 mmol) of [Ir(dppr-dmp)₂Cl]₂ obtained in Step 4, 0.14g (0.78 mmol) of 2,8-dimethyl-4,6-nonanedione (abbreviation: Hdivm),0.28 g (2.6 mmol) of sodium carbonate, and 20 mL of 2-ethoxyethanol wereput into a round-bottom flask equipped with a reflux pipe, and the airin the flask was replaced with argon. After that, irradiation withmicrowaves (2.45 GHz, 120 W) was performed for 1 hour. The solvent wasdistilled off, and the resulting residue was suction-filtered and washedwith methanol.

The obtained solid was dissolved in dichloromethane, and filteredthrough a filter aid in which Celite, alumina, and Celite were stackedin this order. The solvent in the filtrate was distilled off,recrystallization was performed using a mixed solvent of dichloromethaneand methanol, and drying was performed by heating at 200° C.; thus, 0.20g of the organometallic complex [Ir(dppr-dmp)₂(divm)] was obtained as adark red powder in a yield of 37%.

The synthesis scheme of Step 5 is shown in (c-5) below.

Results of analysis of the dark red powder obtained in Step 5 by ¹H-NMRare shown below. A ¹H-NMR chart is shown in FIG. 13. These results showthat [Ir(dppr-dmp)₂(divm)](Structural Formula (312)), which was anorganometallic complex of one embodiment of the present invention, wassynthesized in Step 5.

¹H NMR (CDCl₃, 500 MHz): δ (ppm)=0.60 (dd, 12H), 1.79-1.84 (m, 2H), 1.92(s, 4H), 2.22 (s, 12H), 5.19 (s, 1H), 6.47 (d, 2H), 6.53 (dt, 2H), 6.67(t, 2H), 6.94 (d, 2H), 7.13 (d, 4H), 7.21 (d, 2H), 7.51 (s, 6H), 7.73(s, 4H), 8.48 (s, 2H).

Next, an ultraviolet-visible absorption spectrum (hereinafter, simplyreferred to as an “absorption spectrum”) of a dichloromethane solutionof [Ir(dppr-dmp)₂(divm)] and an emission spectrum thereof were measured.The measurement of the absorption spectrum was conducted on thedichloromethane solution (0.067 mmol/L) in a quartz cell at roomtemperature with an ultraviolet-visible light spectrophotometer (V550type manufactured by JASCO Corporation). The measurement of the emissionspectrum was conducted on the degassed dichloromethane solution (0.067mmol/L) in a quartz cell at room temperature with a fluorescencespectrophotometer (FS920 manufactured by Hamamatsu Photonics K.K.).

Analysis results of the obtained absorption and emission spectra areshown in FIG. 14, in which the horizontal axis represents wavelength andthe vertical axes represent absorption intensity and emission intensity.FIG. 14 shows two solid lines: the thin solid line represents theabsorption spectrum and the thick solid line represents the emissionspectrum. Note that the absorption spectrum in FIG. 14 was obtained bysubtracting the absorption spectrum of dichloromethane from theabsorption spectrum of the dichloromethane solution.

As shown in FIG. 14, the organometallic complex [Ir(dppr-dmp)₂(divm)]has an emission peak at 590 nm, and red-orange light emission wasobserved from the dichloromethane solution.

Next, [Ir(dppr-dmp)₂(divm)] was subjected to a MS analysis by liquidchromatography mass spectrometry (LC/MS).

In the analysis by LC/MS, liquid chromatography (LC) separation wascarried out with ACQUITY UPLC (manufactured by Waters Corporation) andmass spectrometry (MS) analysis was carried out with Xevo G2 Tof MS(manufactured by Waters Corporation).

ACQUITY UPLC BEH C8 (2.1×100 mm, 1.7 μm) was used as a column for the LCseparation, and the column temperature was 40° C. Acetonitrile was usedfor Mobile Phase A and a 0.1% aqueous solution of formic acid was usedfor Mobile Phase B. Further, a sample was prepared in such a manner that[Ir(dppr-dmp)₂(divm)] was dissolved in chloroform at a givenconcentration and the mixture was diluted with acetonitrile. Theinjection amount was 5.0 μL.

In the MS analysis, ionization was carried out by an electrosprayionization (ESI) method. At this time, the capillary voltage and thesample cone voltage were set to 3.0 kV and 30 V, respectively, anddetection was performed in a positive mode. A component with m/z(mass-to-charge ratio) of 1041.61 which underwent the ionization underthe above-described conditions was collided with an argon gas in acollision cell to dissociate into product ions. Energy (collisionenergy) for the collision with argon was 50 eV. The mass range for themeasurement was m/z=100 to 1200. The detection result of the dissociatedproduct ions by time-of-flight (TOF) MS are shown in FIG. 15.

FIG. 15 shows that product ions of [Ir(dppr-dmp)₂(divm)] are mainlydetected around m/z=948 and m/z=863. The results in FIG. 15 showcharacteristics derived from [Ir(dppr-dmp)₂(divm)] and therefore can beregarded as data for identifying [Ir(dppr-dmp)₂(divm)] contained in amixture.

The product ions around m/z=948 are presumed to be cations in the statewhere a methyl group is dissociated from [Ir(dppr-dmp)₂(divm)], whichmeans that [Ir(dppr-dmp)₂(divm)] contains an alkyl group. The productions around m/z=863 are presumed to be cations in the state where Hdivmis dissociated from [Ir(dppr-dmp)₂(divm)], which means that[Ir(dppr-dmp)₂(divm)] contains Hdivm.

Example 4 Synthesis Example 4

Described in this example is a method for synthesizing5,6-bis(4-methylphenyl)-2-pyrazyl triflate (Structural Formula (105))which is one embodiment of the present invention. The structure of5,6-bis(4-methylphenyl)-2-pyrazyl triflate is shown below.

Step 1: Synthesis of 5,6-bis(4-methylphenyl)pyrazin-2-ol

First, 5.5 g (23 mmol) of 4,4′-dimethylbenzil, 3.1 g (28 mmol) ofglycinamide hydrochloride, 2.2 g (55 mmol) of sodium hydroxide, and 120mL of methanol were put into a three-neck flask equipped with a refluxpipe, the air in the flask was replaced with nitrogen, and the mixturewas refluxed for 8.5 hours. Then, stirring was performed until thetemperature of the flask was returned to room temperature. After that, 3mL of 12 M concentrated hydrochloric acid, 2.3 g of potassiumbicarbonate, and 58 mL of water were added to this mixture, andfiltration was performed.

The obtained solid was dried at 100° C. under reduced pressure andrecrystallized with toluene to give 4.8 g of a yellowish white solid ina yield of 75%.

The synthesis scheme of Step 1 is shown in (d-1) below.

Step 2: Synthesis of 5,6-bis(4-methylphenyl)-2-pyrazyl triflate

Into a three-neck flask were put 4.8 g (17 mmol) of5,6-bis(4-methylphenyl)pyrazin-2-ol obtained in Step 1, 174 mL ofdichloromethane, and 4.9 mL of triethylamine. The air in the flask wasreplaced with nitrogen, and 4.3 mL of trifluoromethanesulfonic anhydridewas added dropwise at 0° C. The mixture was stirred at 0° C. for 1.5hours, and further stirred at room temperature for 2 hours.

After the reaction, while the flask was cooled with ice, 60 mL of waterwas added to the mixture, and the organic layer was extracted withdichloromethane. The extract was washed with a saturated aqueoussolution of sodium bicarbonate. Magnesium sulfate was added and gravityfiltration was performed. The solvent in the filtrate was distilled off,and the resulting residue was purified by silica gel columnchromatography using hexane and ethyl acetate in a 1:5 ratio as adeveloping solvent. Thus, 6.27 g of a yellow solid, which was anobjective substance, was obtained in a yield of 88%.

The synthesis scheme of Step 2 is shown in (d-2) below.

Results of analysis of the yellow solid obtained in Step 2 by ¹H-NMR areshown below. A ¹H-NMR chart is shown in FIG. 16. These results show that5,6-bis(4-methylphenyl)-2-pyrazyl triflate, which was one embodiment ofthe present invention, was synthesized in Step 2.

¹H NMR (CD₂Cl₂, 500 MHz): δ (ppm)=2.34 (ds, 6H), 7.11-7.14 (t, 4H),7.31-7.34 (t, 4H), 8.51 (s, 1H).

Example 5 Synthesis Example 5

Described in this example is a synthetic method according to anembodiment of the invention, leading to an organometallic complex,bis{4,6-dimethyl-2-[5-(2,6-dimethylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κN]phenyl-κC}(2,4-pentanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dmdppr-dmp)₂(acac)]), represented by StructuralFormula (301). The structure of [Ir(dmdppr-dmp)₂(acac)] is shown below.

Step: Synthesis of Ir(dmdppr-dmp)₂(acac)

Into a round-bottom flask were put 8.77 g (4.3 mmol) of[Ir(dmdppr-dmp)₂Cl]₂ obtained in Step 4 in Synthesis Example 1 ofExample 1 above, 1.30 g (13.0 mmol) of 2,4-pentanedione (abbreviation:Hacac), 4.60 g (43 mmol) of sodium carbonate, and 44 mL of2-ethoxyethanol, and the mixture was bubbled with argon forapproximately 15 minutes to replace the air in the flask with argon.After that, irradiation with microwaves (2.45 GHz, 400 W) was performedfor 1 hour. The obtained mixture was cooled down to room temperature,and the precipitated solid was obtained by filtration. The obtainedsolid was washed with water and ethanol to give a red solid. This solidwas dried by heating at 100° C. under reduced pressure.

The obtained solid was dissolved in dichloromethane, and filteredthrough a filter aid in which Celite, alumina, and Celite were stackedin this order. The solvent in the filtrate was distilled oftrecrystallization was performed using dichloromethane and ethanol, theresulting solid was dried by heating at 100° C. under reduced pressure,so that 7.49 g of the organometallic complex [Ir(dmdppr-dmp)₂(acac)] wasobtained as a red powdered solid in a yield of 80%.

By a train sublimation method, 3.0 g of the obtained red powdered solid,which was the objective substance, was purified. The sublimationpurification was carried out at 300° C. under a pressure of 3.0 Pa witha flow rate of argon at 13 mL/min. Thus, 2.4 g of the organometalliccomplex [Ir(dmdppr-dmp)₂(acac)] was obtained as a red crystalline solidin a yield of 80%.

The synthesis scheme of the above step is shown in (e) below.

Results of analysis of the red solid obtained in the above step by¹H-NMR are shown below. A ¹H-NMR chart is shown in FIG. 17. Theseresults show that an organometallic complex[Ir(dmdppr-dmp)₂(acac)](Structural Formula (301)) was synthesized in theabove step.

¹H NMR (CDCl₃, 500 MHz): δ (ppm)=1.48 (s, 6H), 1.75 (s, 6H), 1.94 (s,6H), 2.12 (s, 12H), 2.26-2.42 (brs, 12H), 5.18 (s, 1H), 6.48 (s, 2H),6.81 (s, 2H), 7.08 (d, 4H, J=8.0 Hz), 7.12 (s, 2H), 7.18 (t, 2H, J=8.0Hz), 7.30-7.50 (brs, 4H), 8.37 (s, 2H).

Example 6

In this Example, as a comparison with an embodiment of the presentinvention, a conventional synthesis method of [Ir(dmdppr-dmp)₂(acac)] isdescribed. Specifically, a synthesis via a halogen-containingintermediate is described. The synthesis scheme is shown in (f) below.

First, a mixture of 5.00 g of 2,3-dichloropyrazine, 10.23 g of3,5-dimethylphenylboronic acid, 7.19 g of sodium carbonate, 0.29 g ofbis(triphenylphosphine)palladium(II) dichloride (PdCl₂(PPh₃)₂), 20 mL ofwater, and 20 mL of acetonitrile was heated for 60 minutes under argonatmosphere while irradiated with microwaves (2.45 GHz, 100 W).Furthermore, 2.55 g of 3,5-dimethylphenylboronic acid, 1.80 g of sodiumcarbonate, 0.070 g of PdCl₂(PPh₃)₂, 5 mL of water, and 5 mL ofacetonitrile were added, and irradiation with microwaves (2.45 GHz, 100W) was performed again for 60 minutes so that heating was performed. Themixture was added with water, subjected to extraction withdichloromethane, and purified by column chromatography (developingsolvent: hexane:ethyl acetate=5:1 (v/v) and then dichloromethane:ethylacetate=10:1 (v/v)) to give 2,3-bis(3,5-dimethylphenyl)pyrazine(Hdmdppr) as white powder in 44% yield.

Next, 7.8 g of 3-chloroperoxybenzoic acid (mCPBA) was added to adichloromethane (90 mL) solution of 6.6 g of Hdmdppr, stirring wasconducted at room temperature under nitrogen atmosphere for 24 hours,and the reaction solution was poured into water and subjected toextraction with dichloromethane. The extract solution was washed with asaturated aqueous solution of sodium bicarbonate, dried with magnesiumsulfate, filtered, and concentrated to give2,3-bis(3,5-dimethylphenyl)pyrazin-1-oxide as yellow powder in 100%yield.

Then, to 7.0 g of 2,3-bis(3,5-dimethylphenyl)pyrazine-1-oxide was addedphosphoryl chloride, and stirring was performed at 100° C. for 1 hour.The reaction solution was poured into water and extracted withchloroform. The obtained organic layer was washed with a saturatedaqueous solution of sodium bicarbonate, water, and then brine, driedwith magnesium sulfate, filtered, and concentrated to give5-chloro-2,3-bis(3,5-dimethylphenyl)pyrazine as gray powder in 90%yield.

Next, a mixture of 1.21 g of5-chloro-2,3-bis(3,5-dimethylphenyl)pyrazine, 1.10 g of2,6-dimethylphenylboronic acid, 0.78 g of sodium carbonate, 15 mg ofPdCl₂(PPh₃)₂, 14 mL of water, and 14 mL of acetonitrile was degassed bybubbling argon for 15 minutes and irradiated with microwaves (2.45 GHz,100 W) for 3 hours. To the mixture were further added 0.55 g of2,6-dimethylphenylboronic acid, 0.39 g of sodium carbonate, and 7 mg ofPdCl₂(PPh₃)₂, and the mixture was degassed by bubbling argon for 15minutes and heated again by irradiating with microwaves for 6 hours. Themixture was suction-filtered, and the resulting solid was washed withethanol. The obtained solid was dissolved in dichloromethane, which wasfollowed by filtration through Celite, alumina, and Celite in thisorder. The filtrate was concentrated to give5-(2,6-dimethylphenyl)-2,3-bis(3,5-dimethylphenyl)pyrazine as whitepowder in 89% yield. Explanation of the following reactions is omittedbecause they are the same as those in Example 5.

Example 7

In this Example, the purity of [Ir(dmdppr-dmp)₂(acac)] obtained by thesynthesis method of an embodiment of the present invention and thatobtained by the conventional synthesis method were estimated by means ofthe LC/MS analysis. The former was obtained in Example 5, while thelatter was obtained in Example 6. The LC/MS analysis was carried out inthe same way as that of Example 3.

The purity of the organoiridium complex obtained in Example 5 wascalculated to be equal to or higher than 99.9% from the peak area of theLC chromatogram. In contrast, the purity of the organoiridium complexobtained in Example 6 was 99.4%, and 4 chromatogram peaks were observedas impurities. The area ratio of these impurity peaks was approximately1:1:2:2, and the MS analysis of the peaks gave the m/z of 1107, 1105,1109, and 1109, respectively. The difference in molecular weight from[Ir(dmdppr-dmp)₂(acac)] suggests that these peaks result from chlorineadducts of [Ir(dmdppr-dmp)₂(acac)]. Thus, it is concluded that theorganoiridium complex obtained by the conventional synthesis methodusing a halogen-containing intermediate includes halogen adducts asimpurities. The attempts of the inventors failed to completely removethe impurities even though the intermediates were purified.

The aforementioned results lead to a conclusion that the synthesismethod of an embodiment according to the present invention enables thefacile formation of an organometallic complex such as an organoiridiumcomplex in high purity.

Example 8

This Example shows the fabrication and characteristics of alight-emitting element (hereinafter, referred to as Element 1) includingthe organoiridium complex obtained by applying the synthesis method ofan embodiment of the present invention. As a comparative example, thefabrication and characteristics of a comparative light-emitting element(hereinafter, referred to as Reference Element 1) including theorganoiridium complex obtained via the halogen-containing intermediateare also demonstrated. The former organoiridium complex was obtained inExample 5, while the latter one was obtained in Example 6. The structureof these elements is the same as that illustrated in FIG. 1. Thestructures and abbreviations of the compounds used in the elementfabrication are shown below.

<<Fabrication of Element 1>>

Indium tin oxide including silicon oxide (ITSO, thickness: 110 nm, area:2 mm×2 mm) formed over a glass substrate was employed as the firstelectrode 101, over which 1,3,5-tri(dibenzothiophen-4-yl)benzene(DBT3P-II) and molybdenum oxide were co-evaporatively deposited to athickness of 20 nm to form the hole-injection layer 111 where the weightratio of DBT3P-II:MoO₃ was 2:1.

The hole-transport layer 112 with a thickness of 20 nm was formed overthe hole-injection layer 111 by evaporating4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine (BPAFLP).

Over the hole-transport layer 112 was formed the light-emitting layer113 by co-evaporating2-[3′-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline(2mDBTBPDBq-II),N-(1,1′-biphenyl-4-yl)-9,9-dimethyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9H-fluoren-2-amine (PCBBiF), and [Ir(dmdppr-dmp)₂(acac)] to a thickness of 20 nmwhere the weight ratio of 2mDBTBPDBq-II: PCBBiF:[Ir(dmdppr-dmp)₂(acac)]was 0.8:0.2:0.05.

Over the light-emitting layer 113 was formed the electron-transportlayer 114 by sequentially evaporating 2mDBTBPDBq-II andbathophenanthroline (Bphen) to a thickness of 20 nm and 10 nm,respectively. Lithium fluoride and aluminum were evaporated to athickness of 1 nm and 200 nm to respectively form the electron-injectionlayer 115 and the second electrode 103 over the electron-transport layer114. Sealing was carried out by fixing an opposing glass substrate overthe glass substrate with a sealing material, by which Element 1 wasobtained.

<<Fabrication of Reference Element 1>>

Reference Element 1 was fabricated similarly to Element 1 other than thefollowing points: [Ir(dmdppr-dmp)₂(acac)] prepared via thehalogen-containing intermediate was employed;4,4′-di(1-naphthyl)-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine(PCBNBB) was used instead of PCBBiF; and the thickness of the Bphenlayer was 20 nm. The structures of Element 1 and Reference Element 1 areshown in Table 1. Note that the structures of Element 1 and ReferenceElement 1 are different from each other in the second host material ofthe light-emitting layer 113 and the thickness of the Bphen layer.However, the inventors have proven that such a small different does notinfluence the element reliability.

TABLE 1 Structures of Element 1 and Reference Element 1 Element 1Reference Element 1 thickness thickness Layer Ref. (nm) Material ^(a)(nm) Material ^(a) 2nd electrode 103 200 Al 200 Al EIL ^(b) 115 1 LiF 1LiF ETL ^(c) 114 10 Bphen 20 Bphen 20 2mDBTBPDBq-II 20 2mDBTBPDBq-II EmL^(d) 113 20 2mDBTBPDBq-II:PCBBiF:[Ir(dmdppr- 402mDBTBPDBq-II:PCBNBB:[Ir(dmdppr- dmp)₂(acac)] (0.8:0.2:0.05)dmp)₂(acac)] (0.8:0.2:0.05) HTL ^(e) 112 20 BPAFLP 20 BPAFLP HIL ^(f)111 20 DBT3P-II:MoO_(x) 20 DBT3P-II:MoO_(x) (2:1) (2:1) 1st electrode101 110 ITSO 110 ITSO ^(a) Parentheses are weight ratios. ^(b)Electron-injection layer. ^(c) Electron-transport layer. ^(d)Light-emitting layer. ^(e) Hole-transport layer. ^(f) Hole-injectionlayer.

The luminance-current efficiency characteristics, the voltage-luminancecharacteristics, the luminance-external quantum efficiencycharacteristics, and the emission spectra of Element 1 and ReferenceElement 1 are shown in FIGS. 18 to 21, respectively. Almost the sameemission spectra were obtained from both elements, which reveals that[Ir(dmdppr-dmp)₂(acac)] was confirmed to undergo emission. As shown inFIG. 20, the voltage-luminance characteristics of Element 1 andReference Element 1 are almost the same. FIGS. 18 and 19 show thatReference Element 1 exhibits higher efficiency than Element 1 to someextent. However, remarkable difference was not observed.

In contrast, a large difference in reliability was observed betweenElement 1 and Reference Element 1. Specifically, as shown in FIG. 22,the constant-current operation of Reference Element 1 with an initialluminance of 5000 cd/m² at room temperature resulted in a decrease inluminance to less than 70% of the initial value after 300-houroperation. On the other hand, Element 1 maintained more than 70% of theinitial luminance even after the operation for 800 hours.

These results lead to a conclusion that the use of the synthesis methodof an embodiment according to the present invention allows the formationof an organometallic complex in high purity, which contributes to thefabrication of highly reliable light-emitting elements, light-emittingdevices, display devices, and so on.

This application is based on Japanese Patent Application serial no.2013-245957 filed with Japan Patent Office on Nov. 28, 2013, the entirecontents of which are hereby incorporated by reference.

What is claimed is:
 1. A compound represented by the following formula:

wherein R¹ to R⁸ each independently represent any one of hydrogen, an alkyl group having 1 to 6 carbon atoms, a phenyl group, and a phenyl group having, as a substituent, an alkyl group having 1 to 6 carbon atoms.
 2. A synthetic method including: coupling a 5,6-diaryl-2-pyrazyl trifluoromethansulfonate with an arylboronic acid derivative to give a 2,5,6-triarylpyrazine.
 3. The synthetic method according to claim 2, wherein the 5,6-diaryl-2-pyrazyl trifluoromethansulfonate is represented by the following formula:

wherein R¹ to R⁸ each independently represent any one of hydrogen, an alkyl group having 1 to 6 carbon atoms, a phenyl group, and a phenyl group having, as a substituent, an alkyl group having 1 to 6 carbon atoms.
 4. The synthetic method according to claim 2, wherein: the arylboronic acid derivative is represented by the following formula:

the 2,5,6-triarylpyrazine is represented by the following formula:

and R¹ to R¹³ each independently represent any one of hydrogen, an alkyl group having 1 to 6 carbon atoms, a phenyl group, and a phenyl group having, as a substituent, an alkyl group having 1 to 6 carbon atoms.
 5. The synthetic method according to claim 2, wherein the coupling is conducted in the presence of a palladium catalyst.
 6. The synthetic method according to claim 2, further comprising: reacting the 2,5,6-triarylpyrazine with a metal compound to give an ortho-metallated complex.
 7. The synthetic method according to claim 6, wherein the metal compound is iridium chloride.
 8. The synthetic method according to claim 4, further comprising: reacting the 2,5,6-triarylpyrazine with an iridium compound to give a halogen-bridged complex represented by the following formula:

wherein Y is halogen.
 9. The synthetic method according to claim 8, further comprising: reacting the halogen-bridged complex with a ligand to give an ortho-metallated complex.
 10. The synthetic method according to claim 9, wherein: the ortho-metallated complex is represented by the following formula:

and L is a monoanionic ligand.
 11. A method for manufacturing a light-emitting element, the method comprising: coupling a 5,6-diaryl-2-pyrazyl trifluoromethansulfonate with an arylboronic acid derivative to give a 2,5,6-triarylpyrazine; transforming the 2,5,6-triarylpyrazine to an ortho-metallated complex by using a metal compound; forming a layer including the ortho-metallated complex between a pair of electrodes.
 12. The method according to claim 11, wherein the 5,6-diaryl-2-pyrazyl trifluoromethansulfonate is represented by the following formula:

wherein R¹ to R⁸ each independently represent any one of hydrogen, an alkyl group having 1 to 6 carbon atoms, a phenyl group, and a phenyl group having, as a substituent, an alkyl group having 1 to 6 carbon atoms.
 13. The method according to claim 11, wherein: the arylboronic acid derivative is represented by the following formula:

the 2,5,6-triarylpyrazine is represented by the following formula:

and R¹ to R¹³ each independently represent any one of hydrogen, an alkyl group having 1 to 6 carbon atoms, a phenyl group, and a phenyl group having, as a substituent, an alkyl group having 1 to 6 carbon atoms.
 14. The method according to claim 11, wherein the coupling is conducted in the presence of a palladium catalyst.
 15. The method according to claim 11, wherein the metal compound is iridium chloride.
 16. The method according to claim 13, wherein: the ortho-metallated complex is represented by the following formula:

and L is a monoanionic ligand.
 17. The method according to claim 13, wherein: the transformation of the 2,5,6-triarylpyrazine to the ortho-metallated complex includes a reaction of the 2,5,6-triarylpyrazine with iridium chloride to form a halogen-bridged dinuclear complex represented by the following formula:

and Y is halogen.
 18. The method according to claim 17, wherein the transformation of the 2,5,6-triarylpyrazine to the ortho-metallated complex includes a reaction of the halogen-bridged dinuclear complex with a ligand. 